Recurrent duplication-driven transposition
of DNA during hominoid evolution
Matthew E. Johnson*†, NISC Comparative Sequencing Program‡§, Ze Cheng*, V. Anne Morrison¶, Steven Scherer?,
Mario Ventura**, Richard A. Gibbs?, Eric D. Green‡††, and Evan E. Eichler*¶‡‡
*Department of Genome Sciences and the¶Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195;†Department of Genetics and
Center for Human Genetics, Case Western Reserve School of Medicine and University Hospitals of Cleveland, Cleveland, OH 44106;††Genome Technology
Branch and‡NISC, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892;?Human Genome Sequencing Center,
Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030; and **Sezione di Genetica, Dipartimento di Anatomia Patologica e di Genetica,
University of Bari, 70126 Bari, Italy
Edited by Susan R. Wessler, University of Georgia, Athens, GA, and approved August 18, 2006 (received for review July 1, 2006)
The underlying mechanism by which the interspersed pattern of
human segmental duplications has evolved is unknown. Based on
a comparative analysis of primate genomes, we show that a
particular segmental duplication (LCR16a) has been the source
locus for the formation of the majority of intrachromosomal
duplications blocks on human chromosome 16. We provide evi-
dence that this particular segment has been active independently
in each great ape and human lineage at different points during
evolution. Euchromatic sequence that flanks sites of LCR16a inte-
gration are frequently lineage-specific duplications. This process
has mobilized duplication blocks (15–200 kb in size) to new
genomic locations in each species. Breakpoint analysis of lineage-
specific insertions suggests coordinated deletion of repeat-rich
DNA at the target site, in some cases deleting genes in that species.
a segment of DNA becomes duplicated is determined by its prox-
imity to core duplicons, such as LCR16a.
duplicons ? LCR16 elements ? lineage-specific duplications ?
segmental duplications that are interspersed at discrete locations in
the genome (1–5). Although recent duplications are common
among other animal genomes, they are typically organized as
clusters of tandemly arrayed segments (6). In humans and other
great-ape genomes, ?450 duplication hubs have been identified
that have been the target of duplications from many different
ancestral loci. This property has created regions of the genome that
genes, fusion genes, and gene families have emerged (2, 8–13).
that duplications have occurred in a stepwise fashion, involving
mechanism by which hundreds of kilobases of genomic sequence
becomes duplicatively transposed to a new location on a chromo-
some is unknown.
Human chromosome 16 represents one of the most extreme
examples of such recent segmental-duplication activity (15). More
than 10% of the euchromatic portion of human chromosome 16p
consists of segmental duplications known as LCR16 (low-copy
repeat sequences on chromosome 16) (16, 17). During the initial
sequence analysis of this chromosome, Loftus et al. (17) identified
at least 20 distinct gene-rich LCR16 elements, ranging in size from
a few kilobases to ?50 kb in length, termed LCR16a–t. The
majority of these were duplicated in an interspersed configuration
throughout the chromosome. We subsequently identified a gene
family, morpheus, within LCR16a that showed significant signa-
tures of positive selection [Ka?Ks ratios up to 13.0 between humans
and Old-World monkey (OWM) species]. The finished chromo-
some 16 sequence (18) provided the basis for a detailed analysis of
these regions. We investigated the detailed organization of these
ased on the current sequenced animal genomes, human
genomic architecture is unique in the abundance of large
regions among nonhuman primate species by sequencing large-
insert clones from a diverse panel of primates to address questions
among primates, and the relationship of these complex structures
to the rapidly evolving LCR16a segment.
Human LCR16 Genome Organization. In humans, there are 17 com-
23 distinct copies of LCR16a with fewer copies of other flanking
LCR16 segmental duplications (Table 4, which is published as
chromosome 16). Three blocks map to 16q22, whereas the remain-
der are distributed along the short arm of chromosome 16, where
they occupy an estimated 11% of the euchromatin. The duplication
blocks range in size from 604,376 bp (16p12.1?11.2) to solo copies
of the LCR16a element (?19,794 bp in length) (Table 5, which is
1). Of the 11 other LCR16 elements considered in this analysis
(Table 1), all map within 109 kb of an LCR16a duplication. After
excluding ancestral segments, we find only one exception where a
block exists (LCR16uw, Fig. 1 and Table 6, which is published as
(20 kb) LCR16a element. In contrast, two distinct ‘‘solo’’ LCR16a
elements have been identified that are not associated with other
duplicated segments (Table 5), including a single rogue segment
that has been mapped outside of chromosome 16 to human 18p11.
Single-Copy Architecture of OWM Loci. To investigate the evolution-
ary history of these complex genomic regions, we systematically
recovered large-insert genomic clones corresponding to each hu-
man LCR16 segment from five nonhuman primate species includ-
ing chimpanzee, gorilla, orangutan, macaque, and baboon. We
Author contributions: M.E.J. and E.E.E. designed research; M.E.J., N.C.S.P., V.A.M., S.S.,
M.V., R.A.G., and E.D.G. performed research; M.E.J., Z.C., and E.E.E. analyzed data; and
M.E.J. and E.E.E. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
Abbreviation: OWM, Old-World monkey.
database (accession nos: AC092562, AC07264–AC07266, AC097268, AC097270–AC097271,
AC097326–328, AC097330–334, AC117273, AC118583, AC119422, AC144359–AC144362,
AC144462, AC144590, AC144875–AC144877, AC144879–AC144881, AC145000, AC145025,
AC145354, AC145356, AC145400–AC145403, AC146492, AC146844, AC146898, AC146952,
AC148882, AC149436, AC150449, AC153733, and AC154112).
§National Institutes of Health Intramural Sequencing Center (NISC) Comparative Sequenc-
ing Program: Leadership provided by Robert W. Blakesley, Gerard G. Bouffard, Nancy F.
Hansen, Maishali Maskeri, Pamela J. Thomas, and Jennifer C. McDowell.
‡‡To whom correspondence should be addressed. E-mail: firstname.lastname@example.org.
© 2006 by The National Academy of Sciences of the USA
November 21, 2006 ?
vol. 103 ?
designed a total of 12 probes, one corresponding to each of the
LCR16 duplications, and hybridized each independently to avail-
able genomic BAC libraries (Methods). We identified 782 clones
and estimated the copy number and cooccurrence of various
LCR16 segments in these different species (Tables 1 and 6). The
BAC hybridization revealed that the majority (11 of 12) of the
LCR16 elements are single copy in OWM outgroup species (ma-
caque and baboon) (Table 7, which is published as supporting
have occurred in a stepwise fashion, based on the inferred phylo-
genetic relationship of these species (Table 1). We observed a
positional bias in the evolutionary order of these events. LCR16
segmental duplications located more distally from LCR16a, in
general, are predicted to be more recent than those that map in
closer proximity to human LCR16. Finally, we note that certain
-c) consistently cohybridize to the same BACs, including the
single-copy locus within OWM species, suggesting that these dif-
ferent duplicons originated from the same ancestral locus.
Duplication of Great Ape LCR16 Blocks into New Locations. Mapping
and sequencing of LCR16 segmental duplications within primate
genomes has been problematic because the duplications are typi-
cally embedded in large duplication blocks that may exceed 100 kb
in size. For example, in the chimpanzee genome, these regions are
misassembled, are highly fragmented, or correspond to gaps (19).
Large-insert genomic clones, such as BACs, can help circumvent
this problem because BAC-end sequence (BES) may extend be-
yond the duplication blocks to anchor in unique sequence (20).
Such sequence anchors provide information regarding the corre-
sponding map position. We therefore selected 782 BACs for insert
end-sequencing, generating 526 pairs of end-sequence that were
informative for mapping purposes (Table 8, which is published as
supporting information on the PNAS web site). Based on compar-
ative mapping of macaque and baboon for each single-copy locus
of LCR16, we unambiguously determined the most likely ancestral
location of each segmental duplication, which mapped to nine
distinct locations that were consistent between both outgroup
species (Fig. 1; and see Fig. 4, which is published as supporting
Using a similar strategy, we attempted to assign locations for
corresponding loci within ape genomes using BES data. In contrast
to OWMs, we identified multiple loci for each probe, the vast
majority of which associated with LCR16a based on the hybridiza-
tion results. We categorized ape loci as mapping to (i) an ortholo-
gous locus (based on the identification of LCR16 duplications at
that position in human), (ii) an ancestral position (based on map
positions of single copy loci in baboon and macaque), or (iii) a
nonorthologous location (based on the absence of a corresponding
duplication at that position in human) (Tables 2 and 5 and Fig. 4).
We could assign 35 loci to one of these categories, whereas ?27
were ambiguous (end sequences placed in duplicated sequences in
humans or other primates, preventing accurate assignment; see
Methods). We observed a spatial clustering of new insertions. Both
orangutan insertions mapped to a 5-Mb region on human 13q12.1–
13q12.3 (Fig. 4).
Sequence Structure of Nonorthologous Insertions and Lineage-
five nonhuman primate species (Table 2). For each sequence, we
identified the best location in the genome based on alignment of
unique flanking sequence (Methods). Sequence data generated
from both the macaque and baboon unambiguously confirmed
synteny and structure of the most likely ancestral position (Fig. 5,
which is published as supporting information on the PNAS web
the same location (i.e., LCR16at and LCR16uw). We identified a
minimum of six duplication blocks that were present at locations in
ape genomes where there was no evidence of corresponding
ranged in size from 33.4 kb to an estimated ?200 kb, were always
accompanied by a copy of LCR16a. Moreover, PCR breakpoint
analyses (see below) and FISH analyses (data not shown) con-
firmed that these events occurred specifically within each lineage.
We note that the sequenced insertions consist of both LCR16a and
LCR16 elements flanking these regions, suggesting duplicative
into new locations.
During our analysis of these insertions, we observed segments
bars in Figs. 2 and 6, which is published as supporting information
on the PNAS web site). These lineage-specific duplications ranged
number, and structure of LCR16 duplications are depicted within the context
the human genome reference sequence (hg16), BAC-end sequencing, and
complete clone insert sequence of baboon clones. With the exception of the
ancestral loci, duplication blocks are enumerated based on their position
(p–q) on human chromosome 16 (Table 5).
LCR16 organization in human and baboon. The location, copy
Table 1. LCR16 copy number among primates
LCR16 Human Chimpanzee Gorilla Orangutan Macaque Baboon
Copy number was based on experimental hybridization and BAC-end
sequencing results (Methods). Bold type indicates a shift to single copy
*Copy-number estimate was based on the hg16 or rheMac2 sequence
Johnson et al.
November 21, 2006 ?
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in size from a few kb to ?80 kb in length and were frequently
associated with genic regions (Table 9, which is published as
supporting information on the PNAS web site). There are two
important structural properties regarding these lineage-specific
duplications associated with these insertions. First, these lineage-
specific duplications most frequently map at the periphery of
6). These findings are consistent with hybridization (Table 1) and
duplicons accreting at the edges. Second, most of these peripheral
lineage-specific segmental duplications originate from chromo-
recently occurred (Fig. 2d and see Fig. 5u). These associations with
ancestral loci suggest that lineage-specific LCR16 segments origi-
nate in regions of prior LCR16a integration.
As a more direct test of association with LCR16a, we performed
a series of independent hybridization experiments with each of the
eight lineage-specific duplications in orangutan that were not
clones by PCR to determine whether they were associated with
LCR16a in the orangutan (Table 10, which is published as sup-
porting information on the PNAS web site). Seventy-two percent
(100 of 139) of clones detected by using a lineage-specific probe
were also positive for LCR16a. When BES data were used to
eliminate the ancestral locus, we found that 94% (17 of 18) of the
duplicated loci were in association with LCR16a. We found only
one exception where an orangutan-specific duplication had oc-
curred without LCR16a. These data indicate that different intra-
chromosomal euchromatic duplications have emerged at different
locations in a different lineage but focused, once again, around the
LCR16a core. Interestingly, both copy number and sequence
Table 2. Primate segmental duplication BAC sequencing summary
Sixty-two LCR16 BAC clones from five nonhuman primate species were sequenced and aligned to the human
genome. Loci were classified as new insertion or orthologous based on the presence of unique anchors between
position of single loci in baboon and macaque. For 27 clones, the precise map location could not be assigned
because the entire insert consisted of segmental duplications.
*In the case of orangutan, most mapped to chromosome 13 and therefore were ‘‘new’’ insertions with respect
to human and other apes, but the map location could not be further refined by orthologous anchors.
DRF1 and FLJ31795 on chromosome 17q21.31. The new insertion consists of three LCR16 duplicons that are shared between human and chimpanzee (LCR16e,
site are deleted in chimpanzee (Table 3). The extent of duplication of the underlying sequence based on WSSD analysis is shown for human (light blue),
chimpanzee (pink), and orangutan (dark blue) for this and all subsequent images. (b) Chimpanzee-specific insertion (AC149436) of a segmental duplication
mapping to chromosome 16p13.3. The insertion sequence (33,405 bp) consists of LCR16a and a chimpanzee-specific duplication (termed LCR16b?) of 7,403 bp,
which is single-copy in human. A corresponding deletion of the integration site (16,100 bp) deletes the serine protease EOS gene in chimpanzee. (c) A 230-kb
sequence in orangutan that is completely duplicated (dark blue bar). Two different segments flank the LCR16aw segmental duplication, including a 109-kb
segment corresponding to human chromosome 13q34 (chr13:112701583–112831134) and a 99-kb segment from chromosome 16 (chr16:11526252–11625727).
Both segments are unique in chimpanzee and human. (d) Orangutan genomic sequence (AC144879) shows the presence of an inserted duplication complex
corresponding to human 13q12.11 (chr13:19666603–19839556). A 38,344-bp segment corresponding to the site of insertion in human has been deleted. Several
orangutan-specific duplications are noted, including a 21-kb flanking duplication that maps to the corresponding region in human. This property shows that
LCR16a and the ancestral locus (LCR16n?) were associated.
Sequence alignment between human and nonhuman primate LCR16 loci. (a) Chimpanzee-specific insertion (AC097264) of 81,799 bp between genes
www.pnas.org?cgi?doi?10.1073?pnas.0605426103Johnson et al.
divergence decrease in a gradient-like fashion as distance from
LCR16a increases (Fig. 7, which is published as supporting infor-
observe a virtually identical complex mosaic pattern of segmental
duplications and polarity vis-a `-vis LCR16a in different primate
Recurrent and Independent Duplications of LCR16a. Sequencing of
sequences, we constructed a neighbor-joining phylogenetic tree for
each of the 14 human LCR16 duplicons (Fig. 8, which is published
as supporting information on the PNAS web site). The tree
topology and corresponding branch lengths were remarkably con-
sistent with the evolutionary order of events predicted from the
initial hybridization results. The LCR16a phylogenetic analysis
reveals two distinct clades, one monophyletic origin with respect to
human?African ape sequences and a second monophyletic origin
for the orangutan loci (Fig. 6). This finding is consistent with
molecular clock data, which indicate that LCR16a expansions have
occurred independently in each of the two lineages. It is interesting
that, when the duplication architecture is superimposed over the
LCR16a phylogeny, similar block architectures cluster. For exam-
ple, in the case of human, three distinct groups can be recognized
based largely on the presence of flanking LCR16 duplicons
(LCR16b, d, or k?l). These associations supersede relationships
predicted based on orthology, suggesting large-scale genetic ex-
changes since speciation of humans and great apes (21).
The finding of so many independent, recurrent duplications of
the LCR16a segment prompted us to investigate whether there
might be evidence for additional, more ancient copies of LCR16a
that were not originally identified as a result of our threshold for
detection (i.e., ?90% sequence identity). Five additional loci were
discovered, including three nearly full-length copies on chromo-
some 10q22.3 as well as two partial copies on chromosomes
Xp11.22 and 11p15.4 (Fig 9, which is published as supporting
LCR16a structures were embedded within complex duplication
blocks flanked by chromosome-specific segmental duplications.
that these duplications of LCR16a occurred much earlier during
primate evolution (?40 million years) (22). Analysis of the recent
rhesus macaque genome assembly confirmed the presence of
Xp11.22, 11p15.4, and one of the 10q22.3 loci at syntenic positions
to these human copies, confirming duplication of these before the
divergence of the macaque?human lineages.
Junction Analysis. Two types of junctions could be identified based
those that traversed lineage-specific duplications that had not been
observed in humans (termed accretion boundaries) and (ii) those
transitions where the LCR16 duplications were not present at that
locus in human). The latter, termed insertion boundaries, provided
the opportunity to study the architecture of the integration sites
before duplicative transposition.
We generated precise sequence alignments and examined the
repeat content for a total of 12 insertion and 23 accretion bound-
of these boundaries were tested and validated by junction-PCR
amplification and sequencing of the PCR product (Fig. 3). Overall,
?55% (19 of 35) of the junctions showed the presence of an Alu
these, ?95% (18 of 19) corresponded to younger subfamilies (AluS
information on the PNAS web site). This threefold enrichment
confirms previous findings that younger Alu repeat elements are
significantly enriched at the breakpoints of segmental duplication
(23, 24). Because of the lineage-specific nature of the duplications,
donor and acceptor relationships in most cases could be readily
identical) repeat elements.
was clearly documented at a new location in a nonhuman primate
species, we observed a corresponding genomic deletion of the
preintegration site (Figs. 2 and 3). These deletions ranged in size
from 3.4 to 80.1 kb in length (median length ? 5.9 kb) and were
remarkably repeat-rich (77.3%) (Table 3). The evolutionary age of
6.0 kb at the preintegration site with respect to the human reference sequence. PCR breakpoint analysis shows that repeat sequences were present in common
ape ancestors but that insertion was specific to chimpanzee and bonobo. Variability in PCR products is due to insertion and deletion of Alu repeats, which are
common in repeat-rich regions (22, 42). The preintegration locus consists of 92.7% common repeats.
Breakpoint resolution of a chimpanzee insertion. The schematic depicts a segmental duplication insertion of 82 kb and the corresponding deletion of
Johnson et al.
November 21, 2006 ?
vol. 103 ?
no. 47 ?
the corresponding repeat subfamilies and junction PCR indicate
that these complex retroposon repeat structures represent the
ancestral state. In one case, the corresponding segmental duplica-
tion was associated with the deletion of an entire serine protease
gene in chimpanzee (Fig. 2b). This gene deletion was previously
clearly indicate a previously undescribed mechanism underlying its
excision. Although the number of sites is still limited, these data
suggest that coordinated deletion of repeat-rich DNA is a hallmark
feature of de novo segmental duplication.
Our detailed sequence and evolutionary analysis of a subset of
primate segmental duplications reveals unexpected properties re-
garding their origin and expansion. We summarize these properties
and the supporting data and put forward a model for LCR16
segmental duplication and associated structural variation of pri-
Recurrent Duplications. We show that LCR16a has duplicated
chromosome 16 are or have been associated with a full-length copy
of LCR16a. Human and orangutan LCR16a map to different
locations in the two genomes (Fig. 4). More ancient, full-length
copies of the LCR16a element have been identified on different
chromosomes, once again associated with complex regions of
duplication. These data indicate that LCR16a duplications have
an inherent proclivity to duplicate to new locations.
Duplication Polarity. Other LCR16 elements have accumulated in a
stepwise fashion focused around LCR16a to form complex dupli-
cation blocks (Fig. 6). Unlike LCR16a, solitary duplications (i.e.,
not associated with another LCR) are rarely identified for these (in
the one clear case in human, analysis of the structure showed it to
be a deletion of LCR16a) (Fig. 4v). Based on outgroup sequence
data (macaque and baboon), most of these LCR16 elements
originate from ancestral single-copy sequences (Fig. 1). We show
that younger and less abundant duplications accumulate at the
periphery of LCR16a (Fig. 7). In the case of orangutan, a com-
pletely analogous structure of flanking duplications (independent
suggest polarity of duplication around LCR16a.
Ancestral Associations. Our hybridization and sequencing (Tables 1
and 2) data indicate that several of the ancestral loci of intrachro-
mosomal segmental duplication on chromosomes 13 and 16 have
been associated with LCR16a. In gorilla, for example, we find
LCR16a in close proximity to LCRl (although at least in humans,
such an association no longer exists). Two other examples (Figs. 2d
and 4u) indicate that ancestral positions of LCR16 in chimpanzee
and orangutan map in close proximity with LCR16a and are
associated with lineage-specific duplications in these species. We
propose these associations with LCR16a have served to prime
lineage-specific duplications from these regions.
Coordinated Deletion. Our detailed analysis of six new insertions
have shown that, in all six cases, the newer insertions involved the
coordinated deletion of sequences. The preintegration sequences
are highly enriched for common repeat sequences and may be
prone to double-strand breakage events. The coordinated deletion
of target site nucleotides has been observed for several atypical L1
integration events (26, 27) and may implicate single-strand anneal-
ing (SSA) and?or synthesis-dependent annealing (SDSA) (28, 29)
as part of the pathway of segmental duplication.
Core Duplicon-Flanking Transposition Model. We have shown that
LCR16 segmental duplications change in copy number, composi-
These regions of the genome may be loosely classified as a form of
mobile DNA. Unlike typical common repeats (30), however, this
in a lineage-specific manner, into new genomic contexts. The
complex set of data presented here argues that LCR16a has played
an active role in creating the duplication architecture on human
chromosome 16 and orangutan chromosome 13. We propose that
other LCR16 duplications have been duplicated passively, essen-
tially as genetic hitchhikers as part of this process. The association
of LCR16a elements with ancestral loci, especially younger dupli-
cation events, suggests that a property of the sequence itself has the
independently and at different times during human–great ape
evolution. These events are associated with both deletions and
other rearrangement events that have subtly restructured human
and great ape chromosomes during evolution. Core duplicons,
similar to LCR16a, have recently been identified for other chro-
property of the human?great ape genome.
First, the LCR16a sequence may have evolved mechanistically as a
preferred template for gene conversion events to new locations in
for the directional repair of a double-strand breaks in the genome,
richness of the LCR16a cassette would provide the homology to
promote single-strand annealing and?or SDSA. These findings
might explain the coordinated deletion of preintegration sites, the
enrichment of Alu repeats at breakpoints, and the finding that
sequences flanking LCR16a become duplicated. If the LCR16a
sequence carries an inherent enhancer of gene conversion, it is
unclear how the process could be so processive (hundreds of
Table 3. Composition of preintegration sites based on human reference genome (hg16)
accession no. ChrHuman coordinatesSize, kb Repeats, %
*Sequence content of deleted regions in human genome that contain a previously undescribed, lineage-specific segmental duplication
within a nonhuman primate species (PTR, Pan troglodytes; GGO, Gorilla gorilla; PPY, Pongo pygmaeus).
www.pnas.org?cgi?doi?10.1073?pnas.0605426103Johnson et al.
kilobases) or why it, as opposed to other Alu-rich repeat regions of Download full-text
the genome, is the preferred source.
An alternative explanation for the apparent strong association
of new duplications with LCR16a may be as an indirect conse-
quence of intense selection. We have shown previously that the
gene family encoded by LCR16a shows among the strongest
signatures of positive selection among humans and African ape
genes (8). It is possible that the complex pattern of duplication
is simply a consequence of the pressure to produce more
this model completely, because positive selection of the mor-
pheus gene family occurred only among humans and African
apes (Ka?Ks ? 10–13 for exon 2 when compared with the OWM
outgroup). Our data indicate that complex duplicated blocks
have emerged completely independently in the orangutan lin-
eage, where there is no strong evidence of positive selection
(Ka?Ks ? 1.0). Moreover, we have identified more ancient
copies of LCR16a on chromosomes 10 and 11, and the X
chromosome, suggesting that this piece of genetic material was
therefore favor a duplication-driven model of DNA transposi-
tion. This dynamic model for genomic duplication helps to
explain the nonrandom spatial–temporal distribution of segmen-
tal duplications in human and great apes.
Genomic Library Hybridization and BAC End-Sequencing.Large-insert
genomic BAC libraries (minimum 6-fold coverage) from chimpan-
zee (RPCI-43), gorilla (CHORI-255), the orangutan (CHORI-
253), the olive baboon (RPCI-41), and the rhesus macaque
(CHORI-250) were probed by hybridization for each individual
LCR16 duplication (Table 12, which is published as supporting
LCR16-positive BACs were selected, and the inserts were end-
sequenced. Repeat-masked BES was rescored for quality and
mapped against the human genome (MEGABLAST 12PATCh–d
BES–D 3–p 93–F m–UT–s 150–R T).
BAC Sequencing. BACsweresubjectedtoshotgunsequencingatthe
National Institutes of Health Intramural Sequencing Center (34)
and the Baylor College of Medicine Human Genome Sequencing
Center to (35) at least 6-fold sequence redundancy. A subset of
clones (n ? 25) corresponding to potential new insertions were
selected for ordered and oriented sequence assembly.
Sequence Annotation. Nonhuman primate BAC sequence was
compared with human genome sequence by using Miropeats
(36), two?way?mirror (J. Bailey, personal communication), and
ALIGN (37), using parameters optimized for global alignment
of primate sequences (22). The best map location was defined as
nonduplicated flanking unique sequences. If the entire BAC was
duplicated, the most significant correspondence by BLAST
sequence homology was used, and the location was classified as
‘‘ambiguous.’’ We examined the extent of recent duplication
(?94%) for each clone using the whole-genome shotgun se-
quence-detection strategy for human (2), chimpanzee (38), and
orangutan (E.E.E., unpublished data). FISH hybridization was
used to assess duplication?unique status in gorilla (M.V., un-
published data). For simplicity, human chromosome designa-
tions are used for nonhuman map descriptions (39).
PCR Breakpoint Analysis. A subset of breakpoints associated with
lineage-specific insertions were validated by designing PCR assays
across the breakpoint junctions (Table 12) and amplification of
The dense repeat content of many of the breakpoints precluded
design of assays across all insertion breakpoints.
Phylogenetic Analysis. We extracted overlapping sequences corre-
sponding to each of the human segmental duplications from
nonhuman primate sequences and generated multiple sequence
alignments using ClustalW (40) and corresponding neighbor-
joining phylogenetic trees (MEGA). We considered only noncod-
ing sequences by processing the multiple sequence alignments for
corresponding cDNA using MAM software. We used Kimura’s
two-parameter method (41) for all estimates of genetic distance.
We are grateful to Baishali Maskeri, Robert Blakesley, Andy Sharp, and
centers (Baylor College of Medicine and the Washington University
Genome Sequencing Center) for access to genome assembly data
(macaque) and trace sequence data from the chimpanzee and orangutan
before publication. This work was supported in part by National Insti-
tutes of Health (NIH) Grant GM58815 (to E.E.E.) and by the Intramural
Research Program of the National Human Genome Research Institute,
NIH. E.E.E. is an Investigator of the Howard Hughes Medical Institute.
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Johnson et al.
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vol. 103 ?
no. 47 ?