Michael S. Krawczun

New York State Institute for Basic Research in Developmental Disabilities, New York, New York, United States

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Publications (35)152.84 Total impact

  • Annals of the New York Academy of Sciences 12/2006; 477(1):129 - 150. DOI:10.1111/j.1749-6632.1986.tb40329.x · 4.38 Impact Factor
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    ABSTRACT: Cytogenetic and molecular protocols for prenatal ascertainment of the fragile X syndrome and the associated fragile site at Xq27.3 are relatively reliable. Any new diagnostic method which becomes available still elicits much interest. Kimchi-Sarfaty et al. [1991] reported an increase in frequency of endoreduplication and polyploidy in fra(X) lymphoblasts and amniocytes when cultured with methotrexate (MTX) or fluorodeoxyuridine. Recently we analyzed the endoreduplication/polyploidy system using amniotic fluid, chorionic villus, and fibroblasts from fra(X) positive abortus cell cultures and from control samples. We observed no increased expression of endoreduplicated or polyploid cells in fra(X) positive amniocytes after exposure to MTX. The data presented here clearly dispute the value of endoreduplication/polyploid scoring as a diagnostic aid in prenatal fra(X) analysis.
    American Journal of Medical Genetics 04/1992; 43(1-2):149-54. DOI:10.1002/ajmg.1320430123 · 3.23 Impact Factor
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    ABSTRACT: Recently, we detected fra(X)(q27.3) in aminocyte cultures from female identical twins. The pregnant woman did not exhibit fra(X)(q27.3) in whole blood cultures but was the sister of 2 affected brothers. DNA marker analyses showed that she was a carrier of FRAXA. Amniotic fluid cultures (AFCs) from twins A and B exhibited the fragile X [fra(X)] chromosome, but the level of cytogenetic expression was very low in twin A's AFCs. DNA marker studies indicated both twins were carriers of FRAXA. Peripheral umbilical blood sample (PUBS) cultures exhibited fra(X)(q27.3) at a frequency of about 10% for both twins. DNA fingerprinting indicated that the twins were identical, confirming the clinical impression, with a very thin separating amniotic membrane. To our knowledge, this is the only report of prenatal fra(X)(q27.3) detection in female identical twins, and the second report of identical twin detection [Rocchi et al., 1985]. We have diagnosed prenatally fra(X)(q27.3) in 5 female fetuses using AFCs. The average fra(X) frequency was 4% for these positive female fetuses with a range of 0.5% to 8.5%. Follow-up whole blood studies confirmed our original results at an average fra(X) frequency of 25%. In conclusion: 1. Low frequencies, perhaps 1 or 2%, or a few positive cells in AFCs, are likely to increase in magnitude when confirmed in whole blood cultures either pre- or postnatally. 2. It appears likely that the risk is low for false positive results in AFCs when low frequencies of fra(X)(q27.3) are encountered.
    American Journal of Medical Genetics 04/1992; 43(1-2):128-35. DOI:10.1002/ajmg.1320430120 · 3.23 Impact Factor
  • Edmund C. Jenkins · Charlotte J. Duncan · Hong Gu · Marilyn Genovese · Michael S. Krawczun ·
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    ABSTRACT: Short-term whole blood cultures from 9 unrelated male individuals with the fragile X [fra(X)] syndrome were exposed to 5-fluorodeoxyuridine (FUdR). The fra(X) frequency was higher in 8 of 9 cases where the complete medium contained dialyzed fetal bovine serum (DFBS). In 3 of the cases, the fra(X) frequency nearly tripled (e.g., 12/100 to 33/100) while in 2 others, it nearly doubled (e.g., 15/100 to 29/100). When DFBS cultures from 2 other fra(X) individuals were exposed to increasing folic acid concentrations ranging from 2 to 4,000 × 10−6 M, there was virtually no change in fra(X) expression. In 6 of 9 DFBS cultures, the mitotic index decreased, and it increased in 3. Therefore, although the fra(X) frequency increased, in most DFBS cultures the mitotic index decreased. Whether the reduction in mitotic index indicates an inverse correlation between reduced mitotic index and increased fra(X) expression, at least in cultures from some individuals, will be determined by additional studies. In conclusion: (1) medium supplementation with dialyzed fetal bovine serum should be considered when using FUdR for fra(X) identification in order to avoid potentially false negative results; (2) there appears to be no direct correlation between increased mitotic index and increased fra(X) expression in whole blood cultures; (3) increased folic acid concentrations do not affect fra(X) expression when FUdR fra(X) induction is employed; therefore requesting people to refrain from taking vitamins, including folic acid, before fra(X) testing (a practice that still persists in some places) appears unnecessary.
    American Journal of Medical Genetics 04/1992; 43(1-2):155-60. DOI:10.1002/ajmg.1320430124 · 3.23 Impact Factor
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    ABSTRACT: New York State has established a program to screen post-pubertal mentally retarded males for the fragile X [fra(X)] syndrome. The goal of the program is to identify affected males and inform their families of the diagnosis. Females in these families who are at risk for inheriting the mutation will then be able to determine their carrier status and consider that information in making reproductive decisions. Males were evaluated for 10 features of the syndrome by physicians and nurses throughout the state; cytogenetic analysis was carried out on a subset of this population. A total of 1332 males has been screened and chromosome studies have been completed for 489. Forty-three (9%) were positive for fra(X), and an additional 11 other chromosome abnormalities were identified. The 43 patients belonged to 38 families. Of the 24 families who were informed of the diagnosis, 12 consulted genetic counseling centers for follow-up studies and 12 did not.
    American Journal of Medical Genetics 04/1992; 43(1-2):328-32. DOI:10.1002/ajmg.1320430150 · 3.23 Impact Factor
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    ABSTRACT: Cell cultures from 760 whole blood, amniotic fluid, chorionic villus sample, and peripheral umbilical blood sample specimens were exposed to multiple fra(X)(q27.3) induction systems (none had aphidicolin). Fifty-three exhibited the rare fragile site, fra(X)(q27.3) or FRAXA, none of which demonstrated the common fragile site or FRAXD at band Xq27.2. Only one cell in one of the negative whole blood FUdR-treated cultures from a mentally retarded male showed FRAXD. Therefore, it appears that FRAXD occurs very rarely in cultures treated to induce FRAXA since only one positive cell was observed in over 88,000 analyzed. It appears that very low frequencies of fra(X)(q27) can be accounted for only in part by the presence of the common fragile site since only one of 9 cases, each with one fra(X)(q27) positive cell, exhibited FRAXD and the others were FRAXA. After confirmation of FRAXA with direct DNA testing in a large number of low frequency cases, it should be possible to rely on the detection of very low frequencies of fra(X)(q27.3), e.g., 1% with at least 2 positive cells.
    American Journal of Medical Genetics 04/1992; 43(1-2):136-41. DOI:10.1002/ajmg.1320430121 · 3.23 Impact Factor
  • Archives of Clinical Neuropsychology 01/1992; 7(4):349-350. DOI:10.1093/arclin/7.4.349a · 1.99 Impact Factor
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    ABSTRACT: We reviewed the distribution of autosomal fragile sites (FS) and spontaneous chromosome breaks or gaps (CB) at chromosome locations other than those recognized as FS from 100 amniotic fluid samples (AF), 19 chorionic villus samples (CVS), and 5 percutaneous umbilical blood samples (PUBS) referred for fragile X [fra(X)] analysis. We present data on the degree of expression of autosomal fragility in AF, CVS, and PUBS samples, and the relationship between degree of expression and induction system. The most common observed FS were: 3p14, 9p32, and 6q26 in AF; 9q32, 3q27, and 8q22 in CVS; and 3p14, Xq22, and 16q23 in PUBS cases. Distribution of FS and CB, when compared by induction system, was not found to be identical. Our data also indicate that the presence of any particular FS cannot be used as an indicator for the effectiveness of the fra(X) induction system in prenatal samples.
    American Journal of Medical Genetics 02/1991; 38(2‐3):456 - 463. DOI:10.1002/ajmg.1320380264 · 3.23 Impact Factor
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    ABSTRACT: The following guidelines were adopted by an Ad Hoc Committee convened at the Fourth International Workshop on the Fragile X Syndrome and X-Linked Mental Retardation to establish minimum cytogenetic standards for the preparation and analysis of the fragile X chromosome. The intention of the committee was to develop and provide practical standards for the routine cytogenetic detection of the fragile X. The guidelines describe reasonable criteria for effective tissue culture methods for eliciting the Xq27.3 fragile site in vitro and for the analysis of such chromosome preparations.
    American Journal of Medical Genetics 02/1991; 38(2‐3):400 - 403. DOI:10.1002/ajmg.1320380249 · 3.23 Impact Factor
  • E C Jenkins · M S Krawczun · S E Brooks · S L Brooks · S L Sherman · W T Brown ·
    Progress in clinical and biological research 02/1991; 368:27-42.
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    ABSTRACT: The reliable detection of fra(X)(q27.3) in prenatal samples is important for providing genetic counseling. We have identified 5 new cases of prenatal fragile X [fra(X)] detection in 3 chorionic villus sample (CVS) and 2 amniotic fluid (AF) cell cultures. In 4 of the 5 cases, either excess thymidine (THY) or a combination of THY and 5-fluorodeoxyuridine (FUdR) was clearly superior to FUdR alone as fra(X) inducers. Amniocytes from one case were cultured only in RPMI-1640 and later exposed to FUdR or THY separately. They showed only 2% fra(X) while parallel cultures initiated in Chang medium and incubated in RPMI for at least 7 days (recovery) before fra(X) induction exhibited strikingly increased fra(X) frequencies. Chang medium alone will not allow fra(X) induction in AF (Jenkins EC, Brown WT [1986]: “Genetic Disorders and the Fetus: Diagnosis, Prevention and Treatment.” New York: Plenum Press, pp 185–204). Now, using CVS cells, we report that only 1% and 0% fra(X) were detected using FUdR or THY in cells cultured in RPMI for 4 days after removal from Chang medium. Cells with 7 days “recovery” in RPMI exhibited increases from 2 to 6%. Therefore, we have found that Chang medium is very helpful when the appropriate recovery time in another medium is allowed before fra(X) induction. Some false negative reports can be attributed to: induction in Chang medium alone; lack of sufficient recovery time after initiating cells in Chang before induction; and unavailability of the excess THY fra(X) induction system. In conclusion, 1) multiple induction systems, including a combination of FUdR/THY, and 2) initial culture of cells in Chang medium with more than a 4 day recovery period in RPMI or another appropriate medium, enhance optimal conditions for prenatal fra(X) detection. These modifications should reduce the possibility of false negatives thereby improving the reliability of prenatal fra(X) detection.
    American Journal of Medical Genetics 02/1991; 38(2‐3):447 - 452. DOI:10.1002/ajmg.1320380262 · 3.23 Impact Factor
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    ABSTRACT: Most fragile X [fra(X)] males in New York State have not been identified. Hence, a large number of female relatives are unaware of their risks for having an affected child. A program was established in New York State in 1987 to screen for the fra(X) syndrome in mentally retarded males with living relatives. The goal of the program is to identify affected males and inform their families about the diagnosis. In this way relatives would be able to assess their risks for having a fra(X) male. In order to identify the males a screening form was developed to assess 10 features which included physical characteristics, behavior, and family history. Males who exhibited at least 5 of these manifestations were selected for cytogenetic analysis. Any male who had macroorchidism or a family history of mental retardation was also included. A total of 995 males have been screened of which 352 (35%) were selected for cytogenetic analyses. Seventeen (10.5%) of the 161 completed studies were positive for fra(X). A large number of possible female carriers were identified in the families of the propositi. This program identifies fra(X) males in a population of the mentally retarded for whom there had been no previous diagnosis. By using a two-step procedure, it is possible to screen a large population of the mentally retarded for fra(X) without testing each male cytogenetically.
    American Journal of Medical Genetics 02/1991; 38(2‐3):251 - 255. DOI:10.1002/ajmg.1320380218 · 3.23 Impact Factor
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    ABSTRACT: Numerous intraneuronal neurofibrillary tangles and senile (neuritic) plaques are the two characteristic lesions in Alzheimer disease (AD) and adult Down syndrome (DS). Evidence indicates that microtubule assembly is impaired in AD. We studied spindle microtubule repolymerization rates in EBV-transformed lymphoblasts from AD, DS, and control individuals after colcemid exposure. The distinctive arrangement of microtubules in spindle and its size make this structure an obvious choice for study. Recovery trends in the three patient groups differed significantly; in particular, the controls showed an earlier appearance of intact spindle microtubules than AD. Other researchers found similar results using AD fibroblasts. The results from the DS cells were inconsistent and difficult to interpret. It is unclear how the AD microtubules differ from controls, or whether a relationship exists between the altered microtubule repolymerization kinetics observed in this study and the presence of neurofibrillary tangles in AD patients. A difference in repolymerization rates can be the basis for a diagnostic test for AD if it can be verified.
    Alzheimer Disease and Associated Disorders 02/1990; 4(4):203-16. DOI:10.1097/00002093-199040400-00002 · 2.44 Impact Factor
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    ABSTRACT: We have been attempting to develop a consistently reliable internal control to assure the effectiveness of the 5-fluorodeoxyuridine (FUdR) fragile-X [fra(X)] induction system. We carried out a systematic study of whole-blood specimens cultured from 56 individuals from two different laboratories. An analysis of nearly 9,000 cells demonstrated: (1) the importance of establishing baseline levels of fragile sites in each laboratory, and (2) that a combination of common fragile sites (different for each laboratory) could serve as a consistently reliable indicator of the effectiveness of the FUdR fra(X) induction system. It was suggested that a non-FUdR culture(s) should be incorporated into a laboratory's fra(X)-screening protocol, so that if there are any doubts about the effectiveness of the FUdR system a comparison to background or spontaneously occurring fragile sites can be made within the laboratory. Repeat cultures are recommended where no increase in common fragile-site frequency is observed in the FUdR induction system, and where fra(X) was strongly suspected but not found. In addition, the necessity of using more than one fra(X) induction system in whole-blood cultures was demonstrated, including the effectiveness of an FUdR/excess thymidine double-induction system. Finally, 2 cases of apparent mosaicism for Klinefelter syndrome in fra(X) individuals were observed.
    Pathobiology 02/1990; 58(4):236-40. DOI:10.1159/000163591 · 2.48 Impact Factor
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    ABSTRACT: We wish to report that the fragile X (fra(X)) syndrome appears to be as common in autistic females as in similarly affected males. We have previously reported that, in males, the fra(X) syndrome is often associated with autism [Brown et al., 1982a, b; Fisch et al., 1986; Wisniewski et al., 1985]. We have currently screened 363 males referred with an a priori diagnosis of autism and have found 29 fra(X) cases representing 8.0% of the total screened. During the course of our investigation, 33 females with a previous diagnosis of autism (defined by DSM-III [American Psychiatric Association, 1980] criteria) were screened for fra(X). Of these, 4 (12.1%) were positive. This percentage is not significantly different from that in autistic males (X2(1) = .676, p = .41). Two of the affected females were sisters and one other had a brother attending a school for persons with autism. Therefore, the percentage of fra(X) cases from unrelated samples was 3 out of 32 or 9.4%; a number very close to the percentage for males.
    American Journal of Medical Genetics 10/1989; 34(2):302-3. DOI:10.1002/ajmg.1320340240 · 3.23 Impact Factor
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    ABSTRACT: The finding of chromosome mosaicism is one of the most difficult problems in fetal chromosome analysis. Whether the finding indicates true mosaicism or pseudomosaicism must be investigated. Studies detailing the incidence of true mosaicism and pseudomosaicism have been reported (Hsu & Perlis 1984, Bui et al. 1984, Worton & Stern 1984) but do not correlate pseudomosaicism with any particular type of culture media. Benn & Hsu (1985) compared cell growth and chromosome abnormalities in amniotic fluid cell cultures grown in Chang medium and RPMI-1640 medium and found no statistically significant difference in the rate of abnormalities in the two media. We have previously shown that Chang medium exhibited more abnormalities which were not verified in second and third cultures (Masia et al. 1986). In the current study we examined 212 cases grown in both Chang and RPMI-1640 media, and compared apparent single and multiple cell pseudomosaic abnormalities to medium type. The number of observed abnormalities was 22, occurring in 19 of the cases studied. Apparent pseudomosaic chromosome anomalies were observed in 18 Chang cultures and in 4 RPMI-1640 cultures. Statistical analysis found significant correlation between medium type and the degree of observed pseudomosaic cells. We conclude that the rate at which pseudomosaic cells are observed is partly a function of medium type, and in our laboratory Chang medium caused apparent pseudomosaicism at a greater level than RPMI-1640 medium.
    Clinical Genetics 02/1989; 35(2):139-45. DOI:10.1111/j.1399-0004.1989.tb02919.x · 3.93 Impact Factor
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    ABSTRACT: Recently, it was proposed that the constitutive fragile site at 3p14 be used as an "internal control" to indicate the effectiveness of the FUdR fragile site induction system. We have tested this hypothesis by determining the frequency of constitutive fragile sites at 1p31, 3p14, and 16q23 in cultures from 42 known fra(X) individuals. At least 50 cells were analyzed from each case. Seventy-four percent (31/42), 95% (40/42) and 90% (38/42) of the fra(X) individuals exhibited frequencies of less than 4% at constitutive fragile sites 3p14, 1p31 and 16q23, respectively. Of the 42 individuals tested, 12 or 28.6% showed no fragility at any of the 3 sites studied. On the other hand, at least one constitutive fragile site was observed in 50 cells studied from over 70% of the 42 people studied. It is suggested that "positive controls" continue to be used, while at the same time recording all fragile sites to identify a combination of constitutive fragile sites that may serve as an internal control indicator, and that DNA marker studies be used to complement cytogenetic testing.
    American Journal of Medical Genetics 05/1988; 30(1-2):429-34. DOI:10.1002/ajmg.1320300144 · 3.23 Impact Factor
  • Michael S. Krawczun · Edmund C. Jenkins · W. Ted Brown · Wayne P. Silverman ·
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    ABSTRACT: The effect of cell density on expression of the fragile site at (X)(q27.3) in short-term whole-blood cultures from patients with fragile X [fra(X)] or Martin-Bell syndrome was studied. A significant increase in fra(X) frequency was observed in 7 of 8 samples when cell density was decreased. Higher fra(X) frequency was not always noted at below-routine density, but in some cases fra(X) expression was depressed at above-routine density. We conclude that decay of the FUdR effect explains the fact that fra(X) expression is affected by culture density. It is significant that a relationship exists between the two; it suggests that in order to maximize fra(X) expression in cases with low-percentage fra(X) with standard methods, cell density may have to be adjusted. It is possible that in individuals who are normally nonexpressing, such as some obligate female carriers and nonpenetrant males, fra(X) expression may be sensitive to cell density effects.
    American Journal of Medical Genetics 05/1988; 30(1-2):435-42. DOI:10.1002/ajmg.1320300145 · 3.23 Impact Factor
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    ABSTRACT: At least 35 cases of prenatal fra(X) diagnosis have been confirmed and reported. Amniotic fluid, fetal blood and chorion -ic villus samples have exhibited fra(X) (q27.3) in cultures from 26 males and 9 females. Here we have detected fra(X) in female and male amniotic fluid specimens, AF1/fra(X),X and AF2/fra(X),Y, respectively, and a male CVS/fra(X),Y using both FUdR and excess thymidine (THY) to demonstrate the marker chromosome. Both FUdR and THY detected fra(X) and usually FUdR was superior to THY with the exception of placental cultures. It was important to examine more than one culture per protocol since no fra(X) was observed in one AF2 FUdR culture while another exhibited 19.2% expression. Similarly, confirmation studies in lung fibroblast cultures for AF2 exhibited 4.3% fra(X) in one lab while another found negative results. A similar observation in whole blood cultures was also made recently by us. In addition, we have recently experienced our first false negative fra(X),X prenatal diagnosis. We have observed another case where only one cell in 300 exhibited fra(X) where the male fetus was 50% at-risk and was referred to us after the 20th week of gestation by sonography. On the basis of our experience we recommend the following: 1) the excess THY fra(X) induction system is effective but not superior to FUdR; 2) at least two duplicate cultures per induction system should be analyzed for the marker chromosome to avoid the possibility of false-negative diagnosis; 3) where fra(X) is not demonstrated or is present in very low frequencies in CVS and/or amniotic fluid cultures, complementary DNA marker studies and/or fetal blood cultures must be made available; 4) gestational age dating by ultrasonography is recommended as early as possible.
    American Journal of Medical Genetics 05/1988; 30(1-2):329-36. DOI:10.1002/ajmg.1320300133 · 3.23 Impact Factor
  • W T Brown · E C Jenkins · A C Gross · C B Chan · M S Krawczun · C J Duncan · S L Sklower · G S Fisch ·
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    ABSTRACT: The X-linked fragile X [fra(X)] syndrome, associated with a fragile site at Xq27.3, is the most common Mendelian inherited form of mental deficiency. Approximately 1 in 1060 males and 1 in 677 females carry the fra(X) chromosome. However, diagnosis of carrier status can be difficult since about 20% of males and 44% of females are nonpenetrant for mental impairment and/or expression of fra(X). We analyzed DNA from 327 individuals in 23 families segregating fra(X) for linkage to three flanking polymorphic probes: 52A, F9, and ST14. This allowed probable nonpenetrant, transmitting males and carrier females to be identified. A combined linkage analysis was conducted using these families and published probe information on F9 in 27 other families, 52A in six families, and ST14 in five families. The two-point recombination fraction for 52A-F9 was 0.13 (90% confidence interval, 0.10-0.16), for F9-fra(X) was 0.21 (0.17-0.24), and for fra(X)-ST14 was 0.12 (0.07-0.17). Tight linkage between F9 and fra(X) was observed in some families; in others loose linkage was seen suggesting genetic linkage heterogeneity. Risk analysis of carrier status using flanking DNA probes showed that probable nonpenetrant transmitting males were included in families showing both tight and loose linkage. Thus, in contrast to our previous conclusions, it appears that the presence or absence of nonpenetrant, transmitting males in a family is not an indicator of heterogeneity. To determine if heterogeneity was present, we employed the admixture test. Evidence for linkage heterogeneity between F9 and fra(X) was found, significant at P less than 0.0005. Nonsignificant heterogeneity was seen for 52A-F9 linkage. No heterogeneity was found for fra(X)-ST14. The frequency of fra(X) expression was significantly lower in families with tight F9-fra(X) linkage than in families with loose linkage. Cognition appeared to relate to linkage type: affected males in tight linkage families had higher IQs than those in loose linkage families. These findings of genetic heterogeneity can account in part for the high prevalence and apparent high new mutation rate of fra(X). They will affect genetic counseling using RFLPs. An understanding of the basis for genetic heterogeneity in fra(X) will help to clarify the nature of the unusual pattern of inheritance seen in this syndrome.
    Human Genetics 05/1987; 75(4):311-21. DOI:10.1007/BF00284100 · 4.82 Impact Factor