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Biomedical subjects

E M Eicher

Publications and source records attributed to E M Eicher.

At least 19 recordsLinked to original sources
PubMed2000

Defective mesonephric cell migration is associated with abnormal testis cord development in C57BL/6J XY(Mus domesticus) mice.

During the critical period of mouse sex determination, mesenchymal cells migrate from the mesonephros into the adjacent developing testis. This process is thought to initiate cord development and is dependent on Sry. The presence of Sry, however, does not always guarantee normal testis development. For example, transfer of certain Mus domesticus-derived Y chromosomes, i.e., M. domesticus Sry alleles, onto the C57BL/6J (B6) inbred mouse strain results in abnormal testis development. We tested the hypothesis that mesonephric cell migration was impaired in three cases representing a range of aberrant testis development: B6 XY(AKR), B6 XY(POS), and (BXD-21 x B6-Y(POS))F1 XY(POS). In each case, mesonephric cell migration was abnormal. Furthermore, the timing, extent, and position of migrating cells in vitro and cord development in vivo were coincident, supporting the hypothesis that mesonephric cells are critical for cord development. Additional experiments indicated that aberrant testis development results from the inability of Sry(M. domesticus) to initiate normal cell migration, but that downstream signal transduction mechanisms are intact. These experiments provide new insight into the mechanism of C57BL/6J-Y(M. domesticus) sex reversal. We present a model incorporating these findings as they relate to mammalian sex determination.

Animals↗
PubMed2000

Sry induces cell proliferation in the mouse gonad.

Sry is the only gene on the Y chromosome that is required for testis formation in mammals. One of the earliest morphological changes that occurs as a result of Sry expression is a size increase of the rudimentary XY gonad relative to the XX gonad. Using 5'-bromo-2'-deoxyuridine (BrdU) incorporation to label dividing cells, we found that the size increase corresponds with a dramatic increase in somatic cell proliferation in XY gonads, which is not detected in XX gonads. This male-specific proliferation was observed initially in the cells of the coelomic epithelium and occurred in two distinct stages. During the first stage, proliferation in the XY gonad was observed largely in SF1-positive cells and contributed to the Sertoli cell population. During the second stage, proliferation was observed in SF1-negative cells at and below the coelomic epithelium and did not give rise to Sertoli cells. Both stages of proliferation were dependent on Sry and independent of any other genetic differences between male and female gonads, such as X chromosome dosage or other genes on the Y chromosome. The increase in cell proliferation began less than 24 hours after the onset of Sry expression, before the establishment of male-specific gene expression patterns, and before the appearance of any other known male-specific morphological changes in the XY gonad. Therefore, an increase in cell proliferation in the male coelomic epithelium is the earliest identified effect of Sry expression.

Alleles↗
PubMed1999

Three new allelic mouse mutations that cause skeletal overgrowth involve the natriuretic peptide receptor C gene (Npr3).

In 1979, a BALB/cJ mouse was identified with an exceptionally long body. This phenotype was found to be caused by a recessive mutation, designated longjohn (lgj), that mapped to the proximal region of chromosome 15. Several years later, a mouse with a similarly elongated body was identified in an outbred stock after chemical mutagenesis with ethylnitrosourea. This phenotype also was caused by a recessive mutation, designated strigosus (stri). The two mutations were found to be allelic. A third allele was identified in a DBA/2J mouse and was designated longjohn-2J (lgj(2J)). Analysis of skeletal preparations of stri/stri mice indicated that the endochondral ossification process was slightly delayed, resulting in an extended proliferation zone. A recent study reported that mice overexpressing brain natriuretic peptide, one of the members of the natriuretic peptide family, exhibit a skeletal-overgrowth syndrome with endochondral ossification defects. The Npr3 gene coding for type C receptor for natriuretic peptides (NPR-C), which is mainly involved in the clearance of the natriuretic peptides, mapped in the vicinity of our mouse mutations and thus was a candidate gene. The present study reports that all three mutations involve the Npr3 gene and provides evidence in vivo that there is a natriuretic-related bone pathway, underscoring the importance of natriuretic peptide clearance by natriuretic peptide type C receptor.

Alleles↗
PubMed1999

Genetic and physical mapping of the dreher locus on mouse chromosome 1.

Mutations in the mouse dreher (dr) gene cause skeletal defects, hyperactivity, abnormal gait, deafness, white belly spotting, and hypoplasia of Müllerian duct derivatives. To map dr to high resolution, we utilized two crosses. Initially, we analyzed an intersubspecific intercross to construct a detailed genetic map of simple sequence length polymorphism markers within a 6.3-cM region surrounding the dr locus. Subsequently, we analyzed a second intersubspecific intercross segregating for the dr(6J) allele, which positioned dr within a 0.13-cM region between Rxrg and D1Mit370. A physical contig of BAC clones spanning the dr critical region was constructed, and eight potential dr candidate genes were excluded by genetic or physical mapping. Together these results lay the foundation for positional cloning of the dr gene.

Abnormalities, Multiple↗
PubMed1999

Migration of mesonephric cells into the mammalian gonad depends on Sry.

In mammals, the primary step in male sex determination is the initiation of testis development which depends on the expression of the Y-linked testis determining gene, Sry. The mechanisms by which Sry controls this process are unknown. Studies showed that cell migration from the adjacent mesonephros only occurs into XY gonads; however, it was not known whether this effect depended on Sry, another Y-linked gene, or the presence of one versus two X chromosomes. Here we provide genetic proof that Sry is the only Y-linked gene necessary for cell migration into the gonad. Cell migration from the mesonephros into the differentiating gonad is consistently associated with Sty's presence and with testis cord formation, suggesting that cell migration plays a critical role in the initiation of testis cord development. The induction of cell migration represents the earliest signaling pathway yet assigned to Sry.

Animals↗
PubMed1999

The beta3A subunit gene (Ap3b1) of the AP-3 adaptor complex is altered in the mouse hypopigmentation mutant pearl, a model for Hermansky-Pudlak syndrome and night blindness.

Lysosomes, melanosomes and platelet-dense granules are abnormal in the mouse hypopigmentation mutant pearl. The beta3A subunit of the AP-3 adaptor complex, which likely regulates protein trafficking in the trans - Golgi network/endosomal compartments, was identified as a candidate for the pearl gene by a positional/candidate cloning approach. Mutations, including a large internal tandem duplication and a deletion, were identified in two respective pearl alleles and are predicted to abrogate function of the beta3A protein. Significantly lowered expression of altered beta3A transcripts occurred in kidney of both mutant alleles. The several distinct pearl phenotypes suggest novel functions for the AP-3 complex in mammals. These experiments also suggest mutations in AP-3 subunits as a basis for unique forms of human Hermansky-Pudlak syndrome and congenital night blindness, for which the pearl mouse is an appropriate animal model.

Adaptor Protein Complex beta Subunits↗
PubMed1998

Multigenic and imprinting control of ovarian granulosa cell tumorigenesis in mice.

Spontaneous juvenile ovarian granulosa cell (GC) tumors that occur in young girls are similar to GC carcinomas that develop in SWR-derived inbred mice. We analyzed female offspring from a series of matings among SWR and SJL inbred mice for chromosomal loci underlying tumor susceptibility. Intercross F2 female mice were produced by reciprocal matings of (SWR x SJL)F1 and (SJL x SWR)F1 parents. Tumorigenesis in these F2 mice as well as in SWXJ recombinant inbred and congenic strains of mice derived from SWR and SJL showed significant (P < 0.001) association with Gct1, a dominant susceptibility locus on chromosome (CHR) 4 and with Gct2 on CHR 12. Suggestive (P < 0.01) association was found with Gct3 on CHR 15. A fourth susceptibility locus, Gct4 on CHR X, was demonstrated with a strong parent-of-origin effect associated with the paternal genotype. Imprinting and complex interactions among these four loci combine to establish the probability for GC tumorigenesis in this mouse model.

Alleles↗
PubMed1997

DNA sequence analysis of Sry alleles (subgenus Mus) implicates misregulation as the cause of C57BL/6J-Y(POS) sex reversal and defines the SRY functional unit.

The Sry (sex determining region, Y chromosome) open reading frame from mice representing four species of the genus Mus was sequenced in an effort to understand the conditional dysfunction of some M. domesticus Sry alleles when present on the C57BL/6J inbred strain genetic background and to delimit the functionally important protein regions. Twenty-two Sry alleles were sequenced, most from wild-derived Y chromosomes, including 11 M. domesticus alleles, seven M. musculus alleles and two alleles each from the related species M. spicilegus and M. spretus. We found that the HMG domain (high mobility group DNA binding domain) and the unique regions are well conserved, while the glutamine repeat cluster (GRC) region is quite variable. No correlation was found between the predicted protein isoforms and the ability of a Sry allele to allow differentiation of ovarian tissue when on the C57BL/6J genetic background, strongly suggesting that the cause of this sex reversal is not the Sry protein itself, but rather the regulation of SRY expression. Furthermore, our interspecies sequence analysis provides compelling evidence that the M. musculus and M. domesticus SRY functional domain is contained in the first 143 amino acids, which includes the HMG domain and adjacent unique region (UR-2).

Alleles↗
PubMed1996

Genetic localization of Cd63, a member of the transmembrane 4 superfamily, reveals two distinct loci in the mouse genome.

The membrane protein CD63, a molecular marker for early stages of melanoma progression, has been associated with platelet storage pool deficiency disorders (SPD). CD63 localizes to the membranes of platelets, lysosomes, and melanosomes, all of which are affected in a specific subgroup of SPD. The cDNA encoding CD63 detects two closely related sequences that map to different regions of the mouse genome. One locus maps to mouse Chromosome (Chr) 10 in a region that shares linkage homology with the human chromosome encoding human CD63. The second locus maps to mouse Chr 18 in a region that bears no known human CD63-related genes. No SPD has been localized to these regions of either the mouse or the human chromosomes.

Animals↗
PubMed1996

Sex-determining genes on mouse autosomes identified by linkage analysis of C57BL/6J-YPOS sex reversal.

A powerful approach for identifying mammalian primary (gonadal) sex determination genes is the molecular genetic analyses of sex reversal conditions (that is, XX individuals with testicular tissue and XY individuals with ovarian tissue). Here we determined the number and chromosomal location of autosomal and X-linked genes that cause sex reversal in C57BL/6J (B6) mice carrying a Y chromosome of Mus domesticus poschiavinus origin (YPOS). B6 XYPOS mice develop either as females with exclusively ovarian tissue or as true hermaphrodites with ovarian and testicular tissue. In contrast, the YPOS chromosome is fully masculinizing on most other inbred strain backgrounds. B6-YPOS sex reversal appears to result from the incompatibility of the Sry (sex determining region, Y chromosome) allele carried on the YPOS chromosome with B6-derived autosomal or X-linked loci. We found strong evidence for the location of one gene, designated tda1 (testis-determining, autosomal 1), at the distal end of Chromosome (Chr) 4 and a second gene, tda2, in the central region of Chr 2. A third gene, tda3, on Chr 5 is implicated, but the evidence here is not as strong. We suggest that B6 alleles at these loci predispose XYPOS fetuses to ovarian tissue development, but no single locus or combination of loci is necessary and sufficient to cause sex reversal. The TDA proteins may regulate Sry expression or form complexes with the SRY protein to regulate other genes, or the tda genes may be activated or repressed by the SRY protein.

Animals↗
PubMed1995

Sex reversal in C57BL/6J-YPOS mice corrected by a Sry transgene.

C57BL/6J mice carrying a Mus domesticus poschiavinus Y chromosome (YPOS) develop as females with ovarian tissue or as hermaphrodites with ovarian and testicular tissue. We tested the hypothesis that the Y-linked component of this inherited sex reversal is caused by the M. d. poschiavinus Y-linked testis determining gene (symbolized Tdy or Sry) by examining gonadal development in C57BL/6J XYPOS mice carrying a M. musculus allele of Sry as a transgene. We found that in the presence of the transgene, XYPOS mice developed exclusively testicular tissue. This result indicates that the Sry allele carried on the YPOS chromosome is responsible for development of ovarian tissue in the C57BL/6J inbred strain background. We discuss this finding in light of DNA polymorphisms present in Sry alleles carried by various M. domesticus and M. musculus Y chromosomes. In addition, we present a hypothesis concerning the timing of expression of the testicular and ovarian determining genes in the developing fetal gonad based on the organization of ovarian and testicular tissue in ovotestes.

Animals↗
PubMed1995

Ank3 (epithelial ankyrin), a widely distributed new member of the ankyrin gene family and the major ankyrin in kidney, is expressed in alternatively spliced forms, including forms that lack the repeat domain.

We cloned a novel ankyrin, Ank3, from mouse kidney cDNA. The full-length transcript is predicted to encode a 214-kD protein containing an 89 kD, NH2 terminal "repeat" domain; a 65 kD, central "spectrin-binding" domain; and a 56 kD, COOH-terminal "regulatory" domain. The Ank3 gene maps to mouse Chromosome 10, approximately 36 cM from the centromere, a locus distinct from Ank1 and Ank2. Ank3 is the major kidney ankyrin. Multiple transcripts of approximately 7.5, 6.9, 6.3, 5.7, 5.1, and 4.6 kb are highly expressed in kidney where Ank1 and Ank2 mRNAs are barely detectable. The smaller mRNAs (< or = 6.3 kb) lack the entire repeat domain. These transcripts have a unique 5'untranslated region and NH2-terminal sequence and encode a predicted protein of 121 kD. Two small sequences of 21 and 18 amino acids are alternatively spliced at the junction of the repeat and spectrin-binding domains in the larger (> or = 6.9 kb) RNAs. Alternative splicing of a 588 bp sequence (corresponding to a 21.5-kD acidic amino acid sequence) within the regulatory domain also occurs. Ank3 is much more widely expressed than previously described ankyrins. By Northern hybridization or immunocytochemistry, it is present in most epithelial cells, in neuronal axons, in muscle cells, and in megakaryocytes/platelets, macrophages, and the interstitial cells of Leydig (testis). On immunoblots, an antibody raised to a unique regions of the regulatory domain detects multiple Ank3 isoforms in the kidney (215, 200, 170, 120, 105 kD) and in other tissues. The 215/200 kD and 120/105-kD kidney proteins are close to the sizes predicted for the 7.5/6.9- and 6.3/5.7-kb RNAs (with/without the 588-bp acidic insert). Interestingly, it appears that Ank3 exhibits a polarized distribution only in tissues that express the approximately 7.0-kb isoforms, the only isoforms in the kidney that contain the repeat domain. In tissues where smaller transcripts (< or = 6.3 kb) are expressed. Ank3 is diffusely distributed in some or all cells and may be associated with cytoplasmic structures. We conclude that Ank3 is a broadly distributed epithelial ankyrin and is the major ankyrin in the kidney and other tissues, where it plays an important role in the polarized distribution of many integral membrane proteins.

Alternative Splicing↗
PubMed1994

Deletion mapping by immunoselection against the H-Y histocompatibility antigen further resolves the Sxra region of the mouse Y chromosome and reveals complexity of the Hya locus.

A genetic map of the mammalian Y chromosome cannot be produced by standard Mendelian methods because the Y does not participate in meiotic exchange over the majority of its length. However, deletion mapping of the mouse Y chromosome is facilitated by the fact that its short arm carries the histocompatibility-Y (Hya) locus. This locus encodes male-specific (H-Y) antigens that can be selected against in tissue culture by the technique of immunoselection. To produce cells carrying deletions, cytotoxic T lymphocytes (CTLs) specific for H-Y antigens were cocultured with a lymphoblastoid cell line derived from a mouse carrying the portion of the short arm defined by the Sxra translocation on the distal end of its X chromosome. H-Y antigen-loss variant cells that contained Y-specific deletions were identified. Molecular, karyotypic, and immunological analysis of the deletion variants allowed us to define up to 16 ordered intervals and suggested an overall organization of Sxra. The analysis also suggests that at least two and up to five distinct loci encode H-Y antigens.

Animals↗
PubMed1994

The exon-intron structure and chromosomal localization of the mouse macrophage mannose receptor gene Mrc1: identification of a Ricin-like domain at the N-terminus of the receptor.

The macrophage mannose receptor is a transmembrane protein that is expressed on the surface of mature macrophages. The ectodomain of the receptor contains multiple domains, eight of which belong to the calcium-dependent C-type lectin family. The mannose receptor binds to carbohydrate polymers that have a high content of mannose. This property allows this protein to function as a phagocytic receptor that participates in first-line host defense against invading microorganisms. In this paper we describe the intron-exon structure of the mouse macrophage mannose receptor gene which was found to span at least 70 kilobases. We also report the localization of this gene, termed Mrc1, to mouse Chromosome 2. Like its human counterpart, Mrc1 contains 30 exons and 29 introns. A protein module that resembles a subdomain of the B chain of the plant lectin Ricin has been found within the N-terminal cysteine-rich domain of the mannose receptor.

3T3 Cells↗