[Show abstract][Hide abstract] ABSTRACT: A family of Mastermind-like (MAML) genes encodes critical transcriptional co-activators for Notch signaling, an evolutionarily conserved pathway with numerous roles in both development and human diseases. Notch receptors are cleaved upon ligand engagement and the intracellular domain of Notch shuttles to the nucleus. MAMLs form a functional DNA-binding complex with the cleaved Notch receptor and the transcription factor CSL, thereby regulating transcriptional events that are specific to the Notch pathway. Here, we review recent studies that have utilized molecular, cellular and physiological model system strategies to reveal the pivotal roles of the MAML proteins in Notch signaling. Unexpectedly, however, emerging evidence implicate MAML proteins as exciting key transcriptional co-activators in other signal transduction pathways including: muscle differentiation and myopathies (MEF2C), tumor suppressor pathway (p53) and colon carcinoma survival (beta-catenin). Thus, the MAML family appears to function in transcriptional co-activation in a multitude of cellular processes. It is hypothesized that MAML proteins mediate cross-talk among the various signaling pathways and the diverse activities of the MAML proteins converge to impact normal biological processes and human diseases, including cancers.
[Show abstract][Hide abstract] ABSTRACT: The MAML (mastermind-like) proteins are a family of three co-transcriptional regulators that are essential for Notch signaling, a pathway critical for cell fate determination. Though the functions of MAML proteins in normal development remain unresolved, their distinct tissue distributions and differential activities in cooperating with various Notch receptors suggest that they have unique roles. Here we show that mice with a targeted disruption of the Maml1 gene have severe muscular dystrophy. In vitro, Maml1-null embryonic fibroblasts failed to undergo MyoD-induced myogenic differentiation, further suggesting that Maml1 is required for muscle development. Interestingly, overexpression of MAML1 in C2C12 cells dramatically enhanced myotube formation and increased the expression of muscle-specific genes, while RNA interference (RNAi)-mediated MAML1 knockdown abrogated differentiation. Moreover, we determined that MAML1 interacts with MEF2C (myocyte enhancer factor 2C), functioning as its potent co-transcriptional regulator. Surprisingly, however, MAML1's promyogenic effects were completely blocked upon activation of Notch signaling, which was associated with recruitment of MAML1 away from MEF2C to the Notch transcriptional complex. Our study thus reveals novel and nonredundant functions for MAML1: It acts as a coactivator for MEF2C transcription and is essential for proper muscle development. Mechanistically, MAML1 appears to mediate cross-talk between Notch and MEF2 to influence myogenic differentiation.
Genes & Development 04/2006; 20(6):675-88. DOI:10.1101/gad.1383706 · 10.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In many tissues, actin monomers polymerize into actin (thin) filaments of precise lengths. Although the exact mechanisms involved remain unresolved, it is proposed that "molecular rulers" dictate the lengths of the actin filaments. The giant nebulin molecule is a prime candidate for specifying thin filament lengths in striated muscle, but this idea has never been proven. To test this hypothesis, we used RNA interference technology in rat cardiac myocytes. Live cell imaging and triple staining revealed a dramatic elongation of the preexisting thin filaments from their pointed ends upon nebulin knockdown, demonstrating its role in length maintenance; the barbed ends were unaffected. When the thin filaments were depolymerized with latrunculin B, myocytes with decreased nebulin levels reassembled them to unrestricted lengths, demonstrating its importance in length specification. Finally, knockdown of nebulin in skeletal myotubes revealed its involvement in myofibrillogenesis. These data are consistent with nebulin functioning as a thin filament ruler and provide insight into mechanisms dictating macromolecular assembly.
The Journal of Cell Biology 10/2005; 170(6):947-57. DOI:10.1083/jcb.200502158 · 9.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The efficient functioning of striated muscle is dependent upon the proper alignment and coordinated activities of several cytoskeletal networks including myofibrils, microtubules, and intermediate filaments. However, the exact molecular mechanisms dictating their cooperation and contributions during muscle differentiation and maintenance remain unknown. Recently, the muscle specific RING finger (MURF) family members have established themselves as excellent candidates for linking myofibril components (including the giant, multi-functional protein, titin/connectin), with microtubules, intermediate filaments, and nuclear factors. MURF-1, the only family member expressed throughout development, has been implicated in several studies as an ubiquitin ligase that is upregulated in response to multiple stimuli during muscle atrophy. Cell culture studies suggest that MURF-1 specifically has a role in maintaining titin M-line integrity and yeast two-hybrid studies point toward its participation in muscle stress response pathways and gene expression. MURF-2 is developmentally down-regulated and is assembled at the M-line region of the sarcomere and with microtubules. Functionally, its expression is critical for maintenance of the sarcomeric M-line region, specific populations of stable microtubules, desmin and vimentin intermediate filaments, as well as for myoblast fusion and differentiation. A recent study also links MURF-2 to a titin kinase-based protein complex that is reportedly activated upon mechanical signaling. Finally, MURF-3 is developmentally upregulated, associates with microtubules, the sarcomeric M-line (this report) and Z-line, and is required for microtubule stability and myogenesis. Here, we focus on the biochemical and functional properties of this intriguing family of muscle proteins, and discuss how they may tie together titin-mediated myofibril signaling pathways (perhaps involving the titin kinase domain), biomechanical signaling, the muscle stress response, and gene expression.
Journal of Muscle Research and Cell Motility 02/2005; 26(6-8):389-400. DOI:10.1007/s10974-005-9021-x · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The efficient functioning of striated muscle is dependent upon the structure of several cytoskeletal networks including myofibrils, microtubules, and intermediate filaments. However, little is known about how these networks function together during muscle differentiation and maintenance. In vitro studies suggest that members of the muscle-specific RING finger protein family (MURF-1, 2, and 3) act as cytoskeletal adaptors and signaling molecules by associating with myofibril components (including the giant protein, titin), microtubules and/or nuclear factors. We investigated the role of MURF-2, the least-characterized family member, in primary cultures of embryonic chick skeletal and cardiac myocytes. MURF-2 is detected as two species (approximately 55 kDa and approximately 60 kDa) in embryonic muscle, which are down-regulated in adult muscle. Although predominantly located diffusely in the cytoplasm, MURF-2 also colocalizes with a sub-group of microtubules and the M-line region of titin. Reducing MURF-2 levels in cardiac myocytes using antisense oligonucleotides perturbed the structure of stable microtubule populations, the intermediate filament proteins desmin and vimentin, and the sarcomeric M-line region. In contrast, other sarcomeric regions and dynamic microtubules remained unaffected. MURF-2 knock-down studies in skeletal myoblasts also delayed myoblast fusion and myofibrillogenesis. Furthermore, contractile activity was also affected. We speculate that some of the roles of MURF-2 are modulated via titin-based mechanisms.
[Show abstract][Hide abstract] ABSTRACT: CARP, ankrd-2/Arpp, and DARP, are three members of a conserved gene family, referred to here as MARPs (muscle ankyrin repeat proteins). The expression of MARPs is induced upon injury and hypertrophy (CARP), stretch or denervation (ankrd2/Arpp), and during recovery following starvation (DARP), suggesting that they are involved in muscle stress response pathways. Here, we show that MARP family members contain within their ankyrin repeat region a binding site for the myofibrillar elastic protein titin. Within the myofibril, MARPs, myopalladin, and the calpain protease p94 appear to be components of a titin N2A-based signaling complex. Ultrastructural studies demonstrated that all three endogenous MARP proteins co-localize with I-band titin N2A epitopes in adult heart muscle tissues. In cultured fetal rat cardiac myocytes, passive stretch induced differential distribution patterns of CARP and DARP: staining for both proteins was increased in the nucleus and at the I-band region of myofibrils, while DARP staining also increased at intercalated discs. We speculate that the myofibrillar MARPs are regulated by stretch, and that this links titin-N2A-based myofibrillar stress/strain signals to a MARP-based regulation of muscle gene expression.
[Show abstract][Hide abstract] ABSTRACT: Nebulin is a giant, modular sarcomeric protein and although it was discovered over 2 decades ago, it remains one of the most nebulous components of striated muscle. Previously, several groups identified nebulin as the prime candidate molecule for functioning as a "ruler" to specify the precise lengths of the actin (thin) filaments in skeletal muscle, yet this proposal has never been proven. This article reviews the evidence implicating nebulin as a thin filament ruler, including the most recent studies highlighting its potentially extensive isoform diversity and exciting reports revealing its expression in cardiac tissue. Also examined are novel findings indicating that nebulin is actually a multifunctional filament system, perhaps playing roles in signal transduction, contractile regulation, and myofibril force generation; these ideas are especially intriguing given the growing number of mutations in this giant molecule that are associated with human myopathies.
Trends in Cardiovascular Medicine 08/2003; 13(5):195-201. DOI:10.1016/S1050-1738(03)00076-8 · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nebulin is a giant, modular sarcomeric protein and although it was discovered over 2 decades ago, it remains one of the most nebulous components of striated muscle. Previously, several groups identified nebulin as the prime candidate molecule for functioning as a “ruler” to specify the precise lengths of the actin (thin) filaments in skeletal muscle, yet this proposal has never been proven. This article reviews the evidence implicating nebulin as a thin filament ruler, including the most recent studies highlighting its potentially extensive isoform diversity and exciting reports revealing its expression in cardiac tissue. Also examined are novel findings indicating that nebulin is actually a multifunctional filament system, perhaps playing roles in signal transduction, contractile regulation, and myofibril force generation; these ideas are especially intriguing given the growing number of mutations in this giant molecule that are associated with human myopathies.
Trends in Cardiovascular Medicine 07/2003; 13(5):195-201. · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nebulin is a giant (M(r) 750-850kDa), modular sarcomeric protein proposed to regulate the assembly, and to specify the precise lengths of actin (thin) filaments in vertebrate skeletal muscles. Nebulin's potential role as a molecular template is based on its structural and biochemical properties. Its central approximately 700kDa portion associates with actin along the entire length of the thin filament, its N-terminal region extends to thin filament pointed ends, and approximately 80kDa of its C-terminal region integrates within the Z-line lattice. Here, we determined the exon/intron organization of the entire mouse nebulin gene, which contains 165 exons in a 202kb segment. We identified 16 novel exons, 15 of which encode nebulin-repeat motifs (12 from its central region and 3 from its Z-line region). One novel exon shares high sequence homology to the 20 residue repeats of the tight-junction protein, ZO-1. RT-PCR analyses revealed that all 16 novel exons are expressed in mouse skeletal muscle. Surprisingly, we also amplified mRNA transcripts from mouse and human heart cDNA using primers designed along the entire length of nebulin. The expression of cardiac-specific nebulin transcripts was confirmed by in situ hybridization in fetal rat cardiomyocytes and in embryonic Xenopus laevis (frog) heart. On the protein level, antibodies specific for skeletal muscle nebulin's N and C-terminal regions stained isolated rat cardiac myofibrils at the pointed and barbed ends of thin filaments, respectively. These data indicate a conserved molecular layout of the nebulin filament systems in both cardiac and skeletal myofibrils. We propose that thin filament length regulation in cardiac and skeletal muscles may share conserved nebulin-based mechanisms, and that nebulin isoform diversity may contribute to thin filament length differences in cardiac and skeletal muscle.
[Show abstract][Hide abstract] ABSTRACT: The COOH-terminal A168–170 region of the giant sarcomeric protein titin interacts with muscle-specific RING finger-1 (MURF-1). To investigate the functional significance of this interaction, we expressed green fluorescent protein fusion constructs encoding defined fragments of titin's M-line region and MURF-1 in cardiac myocytes. Upon expression of MURF-1 or its central region (containing its titin-binding site), the integrity of titin's M-line region was dramatically disrupted. Disruption of titin's M-line region also resulted in a perturbation of thick filament components, but, surprisingly, not of the NH2-terminal or I-band regions of titin, the Z-lines, or the thin filaments. This specific phenotype also was caused by the expression of titin A168–170. These data suggest that the interaction of titin with MURF-1 is important for the stability of the sarcomeric M-line region.
MURF-1 also binds to ubiquitin-conjugating enzyme-9 and isopeptidase T-3, enzymes involved in small ubiquitin-related modifier–mediated nuclear import, and with glucocorticoid modulatory element binding protein-1 (GMEB-1), a transcriptional regulator. Consistent with our in vitro binding data implicating MURF-1 with nuclear functions, endogenous MURF-1 also was detected in the nuclei of some myocytes. The dual interactions of MURF-1 with titin and GMEB-1 may link myofibril signaling pathways (perhaps including titin's kinase domain) with muscle gene expression.
The Journal of Cell Biology 05/2002; 157(1):125-36. DOI:10.1083/jcb.200108089 · 9.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Striated muscle is an intricate, efficient, and precise machine that contains complex interconnected cytoskeletal networks critical for its contractile activity. The individual units of the sarcomere, the basic contractile unit of myofibrils, include the thin, thick, titin, and nebulin filaments. These filament systems have been investigated intensely for some time, but the details of their functions, as well as how they are connected to other cytoskeletal elements, are just beginning to be elucidated. These investigations have advanced significantly in recent years through the identification of novel sarcomeric and sarcomeric-associated proteins and their subsequent functional analyses in model systems. Mutations in these cytoskeletal components account for a large percentage of human myopathies, and thus insight into the normal functions of these proteins has provided a much needed mechanistic understanding of these disorders. In this review, we highlight the components of striated muscle cytoarchitecture with respect to their interactions, dynamics, links to signaling pathways, and functions. The exciting conclusion is that the striated muscle cytoskeleton, an exquisitely tuned, dynamic molecular machine, is capable of responding to subtle changes in cellular physiology.
Annual Review of Cell and Developmental Biology 02/2002; 18(1):637-706. DOI:10.1146/annurev.cellbio.18.012502.105840 · 16.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe here a novel sarcomeric 145-kD protein, myopalladin, which tethers together the COOH-terminal Src homology 3 domains of nebulin and nebulette with the EF hand motifs of alpha-actinin in vertebrate Z-lines. Myopalladin's nebulin/nebulette and alpha-actinin-binding sites are contained in two distinct regions within its COOH-terminal 90-kD domain. Both sites are highly homologous with those found in palladin, a protein described recently required for actin cytoskeletal assembly (Parast, M.M., and C.A. Otey. 2000. J. Cell Biol. 150:643-656). This suggests that palladin and myopalladin may have conserved roles in stress fiber and Z-line assembly. The NH(2)-terminal region of myopalladin specifically binds to the cardiac ankyrin repeat protein (CARP), a nuclear protein involved in control of muscle gene expression. Immunofluorescence and immunoelectron microscopy studies revealed that myopalladin also colocalized with CARP in the central I-band of striated muscle sarcomeres. Overexpression of myopalladin's NH(2)-terminal CARP-binding region in live cardiac myocytes resulted in severe disruption of all sarcomeric components studied, suggesting that the myopalladin-CARP complex in the central I-band may have an important regulatory role in maintaining sarcomeric integrity. Our data also suggest that myopalladin may link regulatory mechanisms involved in Z-line structure (via alpha-actinin and nebulin/nebulette) to those involved in muscle gene expression (via CARP).
The Journal of Cell Biology 05/2001; 153(2):413-27. · 9.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe here a novel sarcomeric 145-kD protein, myopalladin, which tethers together the COOH-terminal Src homology 3 domains
of nebulin and nebulette with the EF hand motifs of α-actinin in vertebrate Z-lines. Myopalladin's nebulin/nebulette and α-actinin–binding
sites are contained in two distinct regions within its COOH-terminal 90-kD domain. Both sites are highly homologous with those
found in palladin, a protein described recently required for actin cytoskeletal assembly (Parast, M.M., and C.A. Otey. 2000.
J. Cell Biol. 150:643–656). This suggests that palladin and myopalladin may have conserved roles in stress fiber and Z-line assembly. The
NH2-terminal region of myopalladin specifically binds to the cardiac ankyrin repeat protein (CARP), a nuclear protein involved
in control of muscle gene expression. Immunofluorescence and immunoelectron microscopy studies revealed that myopalladin also
colocalized with CARP in the central I-band of striated muscle sarcomeres. Overexpression of myopalladin's NH2-terminal CARP-binding region in live cardiac myocytes resulted in severe disruption of all sarcomeric components studied,
suggesting that the myopalladin–CARP complex in the central I-band may have an important regulatory role in maintaining sarcomeric
integrity. Our data also suggest that myopalladin may link regulatory mechanisms involved in Z-line structure (via α-actinin
and nebulin/nebulette) to those involved in muscle gene expression (via CARP).
The Journal of Cell Biology 04/2001; 153(2):413-428. DOI:10.1083/jcb.153.2.413 · 9.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The giant myofibrillar protein titin contains within its C-terminal region a serine-threonine kinase of unknown function. We have identified a novel muscle specific RING finger protein, referred to as MURF-1, that binds in vitro to the titin repeats A168/A169 adjacent to the titin kinase domain. In myofibrils, MURF-1 is present within the periphery of the M-line lattice in close proximity to titin’s catalytic kinase domain, within the Z-line lattice, and also in soluble form within the cytoplasm. Yeast two-hybrid screens with MURF-1 as a bait identified two other highly homologous MURF proteins, MURF-2 and MURF-3. MURF-1,2,3 proteins are encoded by distinct genes, share highly conserved N-terminal RING domains and in vitro form dimers/heterodimers by shared coiled-coil motifs. Of the MURF family, only MURF-1 interacts with titin repeats A168/A169, whereas MURF-3 has been reported to affect microtubule stability. Association of MURF-1 with M-line titin may potentially modulate titin’s kinase activity similar to other known kinase-associated proteins, whereas differential expression and heterodimerization of MURF1, 2 and 3 may link together titin kinase and microtubule-dependent signal pathways in striated muscles.
[Show abstract][Hide abstract] ABSTRACT: Strict regulation of actin thin filament length is critical for the proper functioning of sarcomeres, the basic contractile units of myofibrils. It has been hypothesized that a molecular template works with actin filament capping proteins to regulate thin filament lengths. Nebulin is a giant protein ( approximately 800 kDa) in skeletal muscle that has been proposed to act as a molecular ruler to specify the thin filament lengths characteristic of different muscles. Tropomodulin (Tmod), a pointed end thin filament capping protein, has been shown to maintain the final length of the thin filaments. Immunofluorescence microscopy revealed that the N-terminal end of nebulin colocalizes with Tmod at the pointed ends of thin filaments. The three extreme N-terminal modules (M1-M2-M3) of nebulin bind specifically to Tmod as demonstrated by blot overlay, bead binding, and solid phase binding assays. These data demonstrate that the N terminus of the nebulin molecule extends to the extreme end of the thin filament and also establish a novel biochemical function for this end. Two Tmod isoforms, erythrocyte Tmod (E-Tmod), expressed in embryonic and slow skeletal muscle, and skeletal Tmod (Sk-Tmod), expressed late in fast skeletal muscle differentiation, bind on overlapping sites to recombinant N-terminal nebulin fragments. Sk-Tmod binds nebulin with higher affinity than E-Tmod does, suggesting that the Tmod/nebulin interaction exhibits isoform specificity. These data provide evidence that Tmod and nebulin may work together as a linked mechanism to control thin filament lengths in skeletal muscle.
[Show abstract][Hide abstract] ABSTRACT: Qa-2 protein, the Ped gene product, is linked to the cell surface by a glycosylphosphatidylinositol (GPI) anchor. Some GPI-linked proteins can be spontaneously incorporated into the membranes of cells via a technique called "protein painting."We investigated whether Qa-2 could be painted onto T cells and embryos and whether the painted protein would be functional.
Incorporation of Qa-2 into the membranes of T cells and embryos was measured by FACScan and Immuno-PCR, respectively. Function of Qa-2 was measured by cell proliferation.
Qa-2 was incorporated by T cells and embryos and was functional.
GPI-linked Qa-2 protein "painted" onto both T cells and preimplantation embryos is functional, as shown by increased proliferation of T cells after cross-linking with anti-Qa-2 antibody, and increased rate of cleavage division of the embryos.
American journal of reproductive immunology (New York, N.Y.: 1989) 08/2000; 44(1):52-8. DOI:10.1111/j.8755-8920.2000.440108.x · 2.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Qa-2 protein, a glycosylphosphatidylinositol (GPI)-linked major histocompatibility complex (MHC) Class Ib molecule found on the surface of mouse T-cells and preimplantation embryos, is the product of the preimplantation embryo development (Ped) gene. The Ped gene regulates the rate of early embryonic development and subsequent embryo survival. T-cells treated with anti-Qa-2 monoclonal antibody (mAb) and cross-linked with a secondary antibody, in the presence of a co-stimulatory signal, undergo increased proliferation. The purpose of this study was to determine whether cross-linking of Qa-2 similarly affects preimplantation embryos. We cross-linked Qa-2 protein on the surface of C57BL/6 2-cell and 8-cell embryos, in the presence of 4/5-phorbol-12-myristate-13-acetate (PMA), and assessed the percentage of embryos reaching the blastocyst stage, the percentage hatching from the zona pellucida, [(3)H-thymidine] incorporation into DNA, and the total number of cells per embryo as measures of embryonic cleavage rate. Both 2-cell and 8-cell embryos increased their cleavage rates 48 h after cross-linking of Qa-2, compared with control embryos (P < 0.05). Our results indicate that a Qa-2 protein cross-linking mechanism may be one way by which this protein regulates the rate of preimplantation mouse embryo development.
Molecular Human Reproduction 06/2000; 6(6):517-22. DOI:10.1093/molehr/6.6.517 · 3.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sarcomeres of cardiac muscle are comprised of numerous proteins organized in an elegantly precise order. The exact mechanism of how these proteins are assembled into myofibrils during heart development is not yet understood, although existing in vitro and in vivo model systems have provided great insight into this complex process. It has been proposed by several groups that the giant elastic protein titin acts as a "molecular template" to orchestrate sarcomeric organization during myofibrillogenesis. Titin's highly modular structure, composed of both repeating and unique domains that interact with a wide spectrum of contractile and regulatory ligands, supports this hypothesis. Recent functional studies have provided clues to the physiological significance of the interaction of titin with several titin-binding proteins in the context of live cardiac cells. Improved models of cardiac myofibril assembly, along with the application of powerful functional studies in live cells, as well as the characterization of additional titin ligands, is likely to reveal surprising new functions for the titin third filament system.
Advances in Experimental Medicine and Biology 02/2000; 481:67-86; discussion 86-8. DOI:10.1007/978-1-4615-4267-4_5 · 1.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Apoptosis, as determined by blastomere and DNA fragmentation, occurs in many preimplantation mouse embryos. To investigate which genes contribute to apoptosis in preimplantation embryos, we used the reverse transcription-polymerase chain reaction to assess mRNA levels for seven genes in the caspase family and seven genes in the BCL-2 family. All caspase mRNAs were detectable in oocytes, while expression in preimplantation embryos varied in a stage-specific manner. An assay for group II caspase enzymatic activity showed that although transcripts for these caspases could not be detected in zygotes, proteolytic activity could be detected in polar bodies, fragmented zygotes, and zygotes treated with staurosporine. This suggests that maternal caspases are inherited during oogenesis. Transcripts for some members of the BCL-2 family could be detected at every stage of preimplantation development. Transcripts for other members were rarely detected. When BCL-2 and BAX protein levels were assessed using immunofluorescence, both proteins were detected in zygotes and in blastocysts. When fragmented blastocysts were compared to normal blastocysts, levels of BCL-2 immunofluorescence tended to be lower in fragmented blastocysts. This result supports a model in which the ratio of BCL-2 to BAX is altered in apoptotic embryos.
Biology of Reproduction 08/1999; 61(1):231-9. · 3.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Qa-2 antigen, the product of the Ped (Preimplantation embryo development) gene, is a glycosylphosphatidylinositol-linked cell surface protein encoded in the Q region of the mouse major histocompatibility complex (MHC). Ped fast (Qa-2+) mouse strains have significantly higher preimplantation embryo cleavage rates both in vivo and in vitro than Ped slow (Qa-2-) mice. In this study, we determined whether the Ped fast phenotype of blastocysts is due to an increased number of blastomeres in the trophectoderm (TE), the inner cell mass (ICM), or both. We also analysed the Ped gene expression pattern, both at the mRNA and at the protein level, in these lineages. Blastocysts were collected from the congenic mouse strains B6.K2 (Qa-2 +) and B6.K1 (Qa-2-). We performed reverse transcription-polymerase chain reaction (PCR) and Immuno-PCR and found that the Ped gene is expressed at the mRNA and protein level in whole embryos and in isolated ICM cells. Lastly, we differentially stained embryos from these strains and found that B6.K2 blastocysts had significantly higher cell numbers (P < 0.05) in both the ICM and in the TE than B6.K1 blastocysts. These results suggest that Qa-2 expression in both the TE and the ICM of blastocysts directly contributes to the Ped phenotype.
Molecular Human Reproduction 10/1998; 4(10):966-71. DOI:10.1093/molehr/4.10.966 · 3.75 Impact Factor