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Y F Lau

Publications and source records attributed to Y F Lau.

At least 37 records · Page 2Linked to original sources
PubMed1993

Identification of the transcriptional unit, structural organization, and promoter sequence of the human sex-determining region Y (SRY) gene, using a reverse genetic approach.

Using a simple strategy involving cosmid-mediated gene transfer, cDNA library construction, and molecular characterization techniques, we have determined the transcriptional unit, structural organization, and promoter sequence of the human sex-determining region Y (SRY) gene, the putative testis-determining factor (TDF) gene on the human Y chromosome. By this approach, a recombinant cosmid harboring the human SRY sequence was isolated and transfected to appropriate tissue-cultured cells. Recombinant cDNA clones were isolated from a cDNA library constructed from poly (A) + RNA of the transfected cells. Comparative studies between the respective cDNAs and the genomic cosmid have provided information regarding the organization of the SRY gene and its mRNAs. The results indicate that the human SRY gene is an intronless gene, produces transcripts of 1.1 kb, and possesses promoter activities in the transfected cells at approximately 310 bp of its upstream sequences.

Amino Acid Sequence↗
PubMed1992

Demonstration of a stage-specific expression of the ZFY protein in fetal mouse testis using anti-peptide antibodies.

The zinc finger Y (Zfy) gene is located on the Y chromosome of all placental mammals. Although it is phylogenetically conserved and is expressed in mouse fetal testis, it is not the sex determining Y (Tdy) gene. To address the possible function of the Zfy gene in mice, the distribution of Zfy protein in fetal mice was investigated by immunocytochemical staining using several specific antisera against synthetic peptides of the mouse Zfy protein. Analysis of various fetal tissues at different embryonic stages demonstrated a specific staining only in fetal testis. In particular, reactive protein was initially observed in male fetal gonads at day 11.5 postcoitum (p.c.). The immuno-staining intensified in fetal testes at day 12 and 12.5 p.c., decreased drastically in those at day 13 and 14 p.c. and became undetectable in those at day 15 p.c. and beyond. The reactive molecules were distributed mostly within the seminiferous tubules of the embryonic testis. The present observations confirm the previous findings with RT-PCR analysis and indicate that Zfy or Zfy-like protein is expressed in stage-specific manner during early testis differentiation. Its location in the seminiferous tubules suggests a possible role in early germ cell development.

Amino Acid Sequence↗
PubMed1992

The musculus-type Y chromosome of the laboratory mouse is of Asian origin.

Mus musculus domesticus, M.m. bactrianus, M.m. musculus, M.m. castaneus, and M.m. molossinus wild mice were investigated for polymorphisms of the Y Chromosome (Chr) genes Zinc finger-Y (Zfy) and Sex-determining region-Y (Sry). Zfy divided the Y Chrs of these mice into domesticus- (domesticus) and musculus-types (musculus, castaneus, molossinus). M.m. bactrianus specimens had both Y Chrs, possibly owing to the introgression of a musculus-type Y into this population. Sry identified a subpopulation of musculus-type Y chromosomes. This subpopulation, designated the molossinus-type, was found in M.m. molossinus, a M. musculus subspecies specimen from northern China (Changchun), and laboratory mice. The cumulative data suggest that M.m. musculus of northern China and Korea are a subpopulation distinct from M.m. musculus of Europe and central China and that this subpopulation invaded Japan, giving rise to M.m. molossinus. Furthermore, the data suggest that the musculus-type Y of the laboratory mouse originated from this subpopulation, corroborating early historical records reporting that Chinese and Japanese mice that were imported into Europe for the pet trade contributed to the genome of the laboratory mouse.

Animals↗
PubMed1992

Isolation of a phylogenetically conserved and testis-specific gene using a monoclonal antibody against the serological H-Y antigen.

Several cDNA clones of a gene termed male-enhanced antigen-2 (Mea-2), have been isolated from a mouse testicular expression cDNA library using a monoclonal histocompatability Y (H-Ys) antibody which detects specific protein(s) present in the mouse testis but not the ovary. The Mea-2 gene is phylogenetically conserved among various mammalian species examined, and is expressed at high levels in adult mouse testis. The expression pattern of Mea-2 is very similar to that of another gene, the male-enhanced antigen-1 (Mea-1), previously isolated using a polyclonal H-Ys antibody. Northern blotting and RT-PCR analyses demonstrated that Mea-2 is also expressed in other adult and fetal mouse organs at low levels. The testis-enhanced expression of this gene is associated with germ cell development at mid- to late-meiotic stages of spermatogenesis. Analysis of an intersubspecies mouse backcross has assigned this gene to chromosome 5, between the loci Gus and Hnf-1.

Animals↗
PubMed1992

Molecular isolation and characterization of an expressed gene from the human Y chromosome.

Using a positional cloning approach, we have isolated an expressed gene from a flow-sorted Y chromosome cosmid library. The isolation of this gene was based on the identification of the Y-231 cosmid that contains CpG rich sequences (HTF islands) in its human insert. The Y-231 cosmid was capable of detecting a 1.3 kb transcript in poly (A)+ RNA samples from human testis. Several cDNA clones were isolated from a human testis cDNA library constructed in lambda gt10. In addition, DNA-mediated gene transfer and restriction enzyme mapping experiments demonstrated that two functional transcriptional units are present within the Y-231 cosmid. DNA sequencing analysis showed that the largest cDNA clone contains 1075 bp of unique sequence and a poly (A) track at the 3' end of the corresponding mRNA. An open reading frame of 762 bp that encodes a predicted protein of 253 amino acids with a calculated molecular weight of 28.9 kD was identified. The Y-231 structural gene encompasses approximately 2.7 kb of genomic sequence and contains six exons that are interrupted by five introns. The Y-231 gene shares very high (97%) identity at the DNA level to a previously described Y-specific gene, testis specific protein Y-encoded (TSPY) gene, suggesting the possibility that these two genes are related, if not identical. However, the TSPY gene has been postulated to be intronless. Further PCR and RT-PCR analyses of these two genes and their transcripts have provided evidence supporting the hypothesis that they are the same gene and are members of a Y-specific repeated gene family containing intronic sequences. The Y-231 (TSPY) gene is conserved in the male genome and expressed in the testis of the chimpanzee, suggesting that it may play an important role in the physiology of this organ in man and the great ape.

Amino Acid Sequence↗
PubMed1992

Unusual distribution of Zfy and Zfx sequences on the sex chromosomes of the wood lemming, a species exhibiting XY sex reversal.

Sex reversal occurs naturally in the wood lemming (Myopus schisticolor) due to the presence in populations of this species of a variant (mutated) X chromosome, designated X*. Thus, X*Y animals develop into females, whereas XY animals develop into normal males. Chromosome mapping by in situ hybridization of DNA sequences homologous to the human ZFY gene localized the wood lemming Zfx sequences to region p12----p11 on both the wild-type X and the mutated X* chromosomes, at or proximal to a presumed breakpoint (Xp12) involved in the generation of the X* chromosome from the normal X, and Zfy sequences along the entire short arm of the Y chromosome. Differences between Zfx and Zfx* were readily detected by Southern blot analysis. However, both the Zfx and Zfx* genes expressed similarly sized transcripts in all adult somatic tissues investigated. Although the precise molecular difference between the Zfx and Zfx* genes is still unknown, their chromosomal location suggests that either Zfx or some other closely linked gene(s) on the X chromosome may be a major X-linked sex-determining gene, Tdx, which in the X* chromosome fails to interact properly with the Y-linked testis-determining gene, Tdy, thus causing X*Y embryos to develop into females. At least 15 copies of wood lemming Zfy sequences are distributed along the short arm of the Y chromosome. Northern hybridization analyses of adult tissues and somatic cell lines indicated that these Zfy repeats were transcriptionally inactive. Normally, 3-kb Zfy (ZFY) transcripts are readily detected in mouse and human testes, especially in the germ cells. It has therefore been postulated that expression of the Zfy (ZFY) gene may be important for spermatogenesis. Whether the lack of sufficient Zfy transcripts in the testis of the adult wood lemming has any impact on spermatogenesis in this species is still to be elucidated by further studies.

Animals↗
PubMed1990

Stage-specific expression of the lactate dehydrogenase-X gene in adult and developing mouse testes.

Lactate dehydrogenase-X (LDH-X), a glycolytic enzyme found only in mammalian testes and spermatozoa, is encoded by a single gene (Ldh-x) in the mouse haploid genome. Several studies have demonstrated that LDH-X is associated with germ cells at specific stages of development. We have examined the expression of the Ldh-x gene during mouse spermatogenesis and testis maturation using in situ mRNA hybridization and immunocytochemistry. The results showed that transcription and translation of the Ldh-x gene are initiated at the pachytene stage of germ cell differentiation. However, although the amount of LDH-X protein increased as the germ cells progressed to maturation, its mRNA level was greatly decreased. These observations were confirmed by Northern analysis of total RNA derived from fractionated spermatogenic cells and developing testes. Furthermore, Northern studies also indicated two sizes of Ldh-x transcripts among different populations of spermatogenic cells in mature mouse testis.

Animals↗
PubMed1990

Molecular cloning of an acrosomal sperm antigen gene and the production of its recombinant protein for immunocontraceptive vaccine.

A monoclonal antibody, HS-63, which reacts specifically with a highly conserved sperm acrosome antigen, was shown to inhibit in vitro fertilization of mouse and human. The corresponding sperm antigen designated as MSA-63 was purified to homogeneity from mouse testes and used as an immunogen to generate polyclonal antisera in rabbits. The cDNA fragments of MSA-63 gene were cloned from mouse testis cDNA library by an immunoscreening method using polyclonal antisera specific for MSA-63. Using the established cDNA clone as a probe, the gene encoding for MSA-63 protein was found to be conserved among different mammalian species. Only one specific mRNA 1.5 kb in size was identified from the adult mouse testis among different mouse tissues. The recombinant fusion protein containing MSA-63 protein fragment was produced in Escherichia coli and used to immunize female mice. Similar to the original HS-63 monoclonal antibody, the antisera thus produced reacted only with the sperm acrosome and revealed significant inhibition to the in vitro fertilization of mouse oocytes. The results of this preliminary study suggest that it is feasible to mass produce sperm-specific antigens or their antigenic fragments by recombinant DNA technology for the development of sperm antigen-based immunocontraceptive vaccines.

Acrosome↗
PubMed1990

The two candidate testis-determining Y genes (Zfy-1 and Zfy-2) are differentially expressed in fetal and adult mouse tissues.

The candidate testis-determining Y genes of the mouse Zfy-1 and Zfy-2, encode proteins containing an acidic amino terminus and a carboxyl terminus composed of 13 zinc fingers. The zinc finger domain is conserved among human and mouse zinc finger X and Y genes. We report a 6-amino-acid deletion in the Zfy-2 zinc finger domain of laboratory mice possessing musculus Y chromosomes. The effect of this deletion on the function of Zfy-2 is not known. The reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot techniques were used to study expression of Zfy in adults and fetuses. In adults, the data suggest that Zfy-1 and Zfy-2 transcription is linked to spermatogenesis, that transcription increases with the initiation of meiosis, and that high levels of these mRNAs are found in postmeiotic round spermatid cells. The data also suggest that differential expression of these two genes is present with expression of Zfy-2 being slightly greater than Zfy-1. In fetuses, Zfy transcripts were detected in several tissues, including the testes. In contrast to the situation in adults, the data suggest that expression of Zfy-1 is greater than that of Zfy-2. The data suggesting that Zfy-1 expression is present in fetal testes support the hypothesis that this gene plays a role in testis differentiation. However, because the Zfy genes are apparently also expressed during spermatogenesis and in fetal organs other than testes, they may serve additional functions besides their postulated role in testis determination.

Animals↗
PubMed1990

Regional assignments of the zinc finger Y-linked gene (ZFY) and related sequences on human and mouse chromosomes.

Recent chromosome walking experiments have identified a candidate gene (ZFY) for the testis-determining factor on the human Y chromosome (Page et al., 1987). We report here the regional assignments of the ZFY gene and related sequences in the human and the mouse. By in situ hybridization, we assigned ZFX and ZFY to human chromosome bands Xp21 and Yp11.3, respectively. Although the mouse harbors two Zfy genes, only one site at band A1 of its Y chromosome was significantly labeled. The mouse Zfx gene and the Zfa gene on chromosome 10 were assigned to bands XD and 10B5, respectively. These assignments of the ZFX gene in human and mouse add another marker to the conserved syntenic group for evaluating the evolutionary relationship of the human and mouse X chromosomes.

Animals↗
PubMed1989

Chromosome mapping and expression of a putative testis-determining gene in mouse.

Isolation and mapping of a mouse complementary DNA sequence (mouse Y-finger) encoding a multiple, potential zinc-binding, finger protein homologous to the candidate human testis-determining factor gene is reported. Four similar sequences were identified in Hind III-digested mouse genomic DNA. Two (7.2 and 2.0 kb) were mapped to the Y chromosome. Only the 2.0-kb fragment, however, was correlated with testis determination. Polymerase chain reaction analysis suggests both Y loci are transcribed in adult testes. A 3.6-kb fragment was mapped to the X chromosome between the T16H and T6R1 translocation breakpoints, and a fourth (6.0 kb) was mapped to chromosome 10. Hence, mYfin sequences have been duplicated several times in the mouse, although they are not duplicated in humans.

Animals↗
PubMed1989

Isolation and chromosomal localization of the human En-2 gene.

By low stringency hybridization we have isolated from a human cosmid genomic library sequences homologous with a probe from the Drosophila engrailed gene. Partial nucleotide sequence analysis shows a consensus splice acceptor site followed by an open reading frame (ORF) that can encode 104 amino acids; the first 94 amino acids have 71% identity with the Drosophila engrailed protein. The shared region contains a homeo domain and is within the region of engrailed shared with the Drosophila invected gene and the mouse En-1 and En-2 genes. At the amino acid level, the human sequence is 85% identical with the mouse En-1 gene and 100% identical with the mouse En-2 gene. Hybridization against a panel of human-hamster somatic cell hybrids maps this human En-2 gene to chromosome 7, and regional mapping by in situ hybridization to human chromosomes localizes it to region 7q36 at the end of the long arm.

Amino Acid Sequence↗
PubMed1989

Male-enhanced antigen gene is phylogenetically conserved and expressed at late stages of spermatogenesis.

The male-enhanced antigen gene (Mea) was previously isolated from a mouse testicular cDNA library by using a pool of specific antisera against the serological H-Y antigen. The present studies characterize the human and mouse cDNAs and indicate that the MEA gene is conserved at both nucleic acid and protein levels. The corresponding mRNA encodes proteins of 18-20 kDa. The phylogenetic conservation could be extended to other mammalian species by Southern blot analysis. Although the Mea gene was transcribed as a 1-kilobase mRNA in most tissues, it was expressed at the highest level in adult testis. The testis-enhanced expression of the Mea gene was associated with germ cell development at late stages of spermatogenesis. Chromosome walking experiments identified two linked genes, A and B, located within 38 kilobases of human genomic sequence. Like the MEA gene, genes A and B were coordinately transcribed in the testis, which suggests that MEA and genes A and B are members of a gene family. In situ hybridization studies localized the MEA gene to the short arm of human chromosome 6 at band p21.1-21.3, close to the major histocompatibility complex locus. The genetic conservation and testis-specific expression of the MEA gene support the hypothesis that it plays an important role in mammalian spermatogenesis and/or testis development.

Amino Acid Sequence↗
PubMed1989

The putative testis-determining factor and related genes are expressed as discrete-sized transcripts in adult gonadal and somatic tissues.

The zinc-finger-Y (ZFY) gene is a candidate for the testis-determining-factor gene (TDF) on the human Y chromosome and is postulated to initiate testis differentiation during embryogenesis. However, the present study indicates that the ZFY gene and its X homologue (ZFX) are differentially expressed in adult tissues. A human testis-specific ZFY cDNA was isolated and completely sequenced. The corresponding ZFY transcript encodes a protein that has 801 amino acids and a calculated molecular weight of 90.6 kD. Expression analysis demonstrated that ZFY is transcribed primarily as 3- and 5.7-kb mRNA in testis and somatic cells, respectively. In contrast, the ZFX gene is expressed as a 5-kb transcript in the testis and as 6.7- and 8-kb transcripts in both ovarian and somatic tissues. With sets of gene-specific oligonucleotides, the origin and relative amount of the respective transcripts can be demonstrated in both Northern hybridization and reverse transcriptase-polymerase chain reaction analysis. Significantly, the 3-kb ZFY transcript was also detected in other mammalian adult testes. The testis-specific transcription of the ZFY gene hence suggests that it serves a conserved function in this organ.

Adult↗
PubMed1989

The anonymous PAS45 probe detects RFLPs in 13q31.

An anonymous DNA probe PAS45 was isolated. This probe detects an RFLP with two alleles 1 and 2 at the same locus, with the different restriction enzymes (Bg1II, EcoRI, HindIII, PstI, MspI, XbaI). The observed polymorphism is explained by a chromosome rearrangement involving these enzyme cleavage sites. The frequency of alleles 1 and 2 was 0.875 and 0.125, respectively, in a sample of 48 unrelated individuals in France. Codominant inheritance of alleles 1 and 2 was demonstrated in 13 families with 30 offspring. The PAS45 probe was localized on chromosome 13 by somatic cell hybrid analysis and on 13q31 by in situ hybridization. The rearrangement on 13q31 is present in one out of four healthy individuals in France.

Animals↗
PubMed1988

Assignment of human gene encoding testis-specific lactate dehydrogenase C to chromosome 11, region p14.3-p15.5.

The human gene coding for lactate dehydrogenase C (LDHC), a testis-specific isozyme, has been assigned to a refined region of chromosome 11, p14.3-p15.5, in which the lactate dehydrogenase A gene (LDHA) also resides, by using somatic cell hybrids and in situ chromosome hybridization. This assignment clearly indicates the close physical proximity of the LDHC and LDHA genes and supports the evolutionary closeness of these two isozymes.

Animals↗
PubMed1988

Sequences contained within the promoter of the human thymidine kinase gene can direct cell-cycle regulation of heterologous fusion genes.

Recent evidence on the transcriptional regulation of the human thymidine kinase (TK) gene raises the possibility that cell-cycle regulatory sequences may be localized within its promoter. A hybrid gene that combines the TK 5' flanking sequence and the coding region of the bacterial neomycin-resistance gene (neo) has been constructed. Upon transfection into a hamster fibroblast cell line K12, the hybrid gene exhibits cell-cycle-dependent expression. Deletion analysis reveals that the region important for cell-cycle regulation is within -441 to -63 nucleotides from the transcriptional initiation site. This region (-441 to -63) also confers cell-cycle regulation to the herpes simplex virus thymidine kinase (HSVtk) promoter, which is not expressed in a cell-cycle manner. We conclude that the -441 to -63 sequence within the human TK promoter is important for cell-cycle-dependent expression.

Base Sequence↗