Biomedical subjects

Yi-Nan Lin

Publications and source records attributed to Yi-Nan Lin.

8 recordsLinked to original sources

PubMed2006

Mining the oocyte transcriptome.

Mammalian folliculogenesis and oocyte physiology are complex and not fully understood. However, major advances over the past 15 years in our ability to create and study in vivo models have improved our understanding of these essential physiological processes. More recently, the availability of vast arrays of DNA sequence information in the forms of "complete" genomes, expressed sequence tag libraries and microarray data from reproductive tissues have stimulated the discovery of new information through genome scanning, prediction programs and in silico screening techniques. These technological improvements will help to expand our understanding of folliculogenesis and oocyte physiology and improve human reproductive health.

Bone Morphogenetic Protein 15↗

PubMed2006

TEX14 is essential for intercellular bridges and fertility in male mice.

Cytokinesis in somatic cells concludes with the formation of a midbody, which is abscised to form individual daughter cells. In contrast, germ cell cytokinesis results in a permanent intercellular bridge connecting the daughter cells through a large cytoplasmic channel. During spermatogenesis, proposed roles for the intercellular bridge include germ cell communication, synchronization, and chromosome dosage compensation in haploid cells. Although several essential components of the midbody have recently been identified, essential components of the vertebrate germ cell intercellular bridge have until now not been described. Herein, we show that testis-expressed gene 14 (TEX14) is a novel protein that localizes to germ cell intercellular bridges. In the absence of TEX14, intercellular bridges are not observed by using electron microscopy and other markers. Spermatogenesis in Tex14(-/-) mice progresses through the transit amplification of diploid spermatogonia and the expression of early meiotic markers but halts before the completion of the first meiotic division. Thus, TEX14 is required for intercellular bridges in vertebrate germ cells, and these studies provide evidence that the intercellular bridge is essential for spermatogenesis and fertility.

Alleles↗

PubMed2006

Regulation of growth differentiation factor 9 expression in oocytes in vivo: a key role of the E-box.

Growth differentiation factor 9 (GDF9) is preferentially expressed in oocytes and is essential for female fertility. To identify regulatory elements that confer high-level expression of GDF9 in the ovary but repression in other tissues, we generated transgenic mice in which regions of the Gdf9 locus were fused to reporter genes. Two transgenes (-10.7/+5.6mGdf9-GFP) and (-3.3/+5.6mGdf9-GFP) that contained sequences either 10.7 or 3.3 kb upstream and 5.6 kb downstream of the Gdf9 initiation codon demonstrated expression specifically in oocytes, thereby mimicking endogenous Gdf9 expression. In contrast, transgenes -10.7mGdf9-Luc and -3.3mGdf9-Luc, which lacked the downstream 5.6-kb region, demonstrated reporter expression not only in oocytes but also high expression in male germ cells. This suggests that the downstream 5.6-kb sequence contains a testis-specific repressor element and that 3.3 kb of 5'-flanking sequence contains all the cis-acting elements for directing high expression of Gdf9 to female (and male) germ cells. To define sequences responsible for oocyte expression of Gdf9, we analyzed sequences of Gdf9 genes from 16 mammalian species. The approximately 400 proximal base pairs upstream of these Gdf9 genes are highly conserved and contain a perfectly conserved E-box (CAGCTG) sequence. When this 400-bp region was placed upstream of a luciferase reporter (-0.4mGdf9-Luc), oocyte-specific expression was observed. However, a similar transgene construct (-0.4MUT-mGdf9-Luc) with a mutation in the E-box abolished oocyte expression. Likewise, the presence of an E-box mutation in a longer construct (-3.3MUT-mGdf9-Luc) abolished expression in the ovary but not in the testis. These observations indicate that the E-box is a key regulatory sequence for Gdf9 expression in the ovary.

Animals↗

PubMed2006

Acrosome-specific gene AEP1: identification, characterization and roles in spermatogenesis.

Spermatogenesis is a tightly regulated process leading to the development of spermatozoa. To elucidate the molecular spermatogenic mechanisms, we identified an acrosome-specific gene AEP1 in spermatids, which is located in rat chromosome 17p14 with a transcript size of 3,091 bp encoding a signal peptide, zinc finger-like motif, coiled-coil region, several predicted glycosylation and phosphorylation sites. Northern blot and RT-PCR analyses revealed the restricted expression of AEP1 to the testis only. In postnatal rat testes, AEP1 mRNA became detectable from postnatal 25 dpp (round spermatids) and onwards. By using in situ hybridization (ISH) and flow cytometry-fluorescent ISH, only the haploid spermatids yielded the positive AEP1 signal. Immunohistochemistry showed that AEP1 was expressed in the acrosomal cap of late-staged germ cells in rat testis, and co-localized with the acrosomal marker, peanut agglutinin. The spatial expression of AEP1 immunoreactivity in testis was conserved among diverse mammalian species (rat, pig, monkey, human). To further study its roles in spermatogenesis, we showed AEP1 and beta-actin was associated together in complex by co-immunoprecipitation in adult germ cells and by immunofluorescence assay in isolated spermatozoon. In human testes diagnosed with hypospermatogenesis, lower expression of AEP1 was observed, whereas there was no detectable signal in undescended testes. In short, AEP1 is an evolutionary-conserved acrosome-specific gene and likely functions in acrosome-cap formation.

Acrosome↗

PubMed2006

Shaping the sperm head: an ER enzyme leaves its mark.

Lipid storage diseases are debilitating inherited metabolic disorders that stem from the absence of specific lysosomal enzymes that degrade selected lipids. Most characteristically, these disorders affect the nervous and the reticulo-endothelial systems, with massive organomegaly resulting from the presence of engorged, lipid-laden macrophages. In this issue of the JCI, Yildiz et al. describe the role of the ER-resident enzyme beta-glucosidase 2 (GBA2) in mice (see the related article beginning on page 2985). Surprisingly, GBA2 deficiency leaves bile acid and cholesterol metabolism intact, instead causing lipid accumulation in the ER of testicular Sertoli cells, round-headed sperm (globozoospermia), and impaired male fertility.

Animals↗

PubMed2005

Genetic manipulations to study reproduction.

Fertility disorders affect approximately 15% of individuals worldwide. With the imminent completion of the human and mouse genome sequence, it will be more feasible to identify the relevant genes underlying many fertility disorders. Already, the mouse has been utilized extensively as a genetic tool for the dissection of gene function, often providing significant insights into the relationship between gene and disease. In fact, there are over 200 mouse models that display reproductive defects. However, the available mouse mutant resources provide functional information for a mere 10% of the total number of genes in the mouse or human genomes at best. The improvement of available genome annotations together with more powerful techniques to manipulate the mouse genome provide substantial improvements in our ability to identify genes involved in reproduction, and in the future will likely benefit patients with fertility problems.

Animals↗

PubMed2005

High-throughput discovery of germ-cell-specific genes.

As a specialized cell population that plays the unique role of transmitting genetic information to subsequent generations, germ cells have been intensively studied to unravel their unique physiology from the specification of primordial germ cells to the fateful reunion of gametes during fertilization. For their differential expression, germ-cell-specific genes are the keys to understanding these unique features. In the last decade, the emerging methodologies designed for large-scale and high-throughput analysis have created an ever-increasing amount of data. Among these methodologies, expressed sequence tag libraries, serial analysis of gene expression, and microarrays provide valuable expression data that can be further analyzed. Using the mouse as a model system, we describe a strategy starting from the quick identification of germ-cell-specific genes using public domain expression data to the functional characterization of the identified genes using targeted gene disruption. This strategy should accelerate the process to fill in the missing pieces of the germ cell physiology puzzle and the construction of genetic networks to help us to understand the etiology of infertility. Furthermore, these identified germ-cell-specific genes may lead to the development of new contraceptives targeted specifically to germ cells.

Animals↗

PubMed2003

Sequence and expression of testis-expressed gene 14 (Tex14): a gene encoding a protein kinase preferentially expressed during spermatogenesis.

To discover germ cell-specific genes, we used in silico subtraction and identified testis expressed gene 14 (Tex14). Mouse Tex14 contains an open reading frame encoding a 1450-amino-acid protein, which shares 64% amino acid identity with the predicted human TEX14 protein. The predicted TEX14 amino acid sequence consists of three ankyrin repeats, a protein kinase domain, and a leucine zipper dimerization motif. Northern blot analysis and in situ hybridization show that Tex14 mRNA is expressed specifically in the testis, with highest levels observed in pachytene, diplotene, and meiotically dividing spermatocytes. Two 5' splice variants of mouse Tex14 were discovered by sequencing 5'-RACE polymerase chain reaction products. TEX14 is predicted to be localized to the nucleus, suggesting that it may play a key role in regulating gene expression or modulating nuclear events during mammalian spermatogenesis.

Amino Acid Sequence↗