Human testis-specific lactate dehydrogenase-C promoter drives overexpression of mouse lactate dehydrogenase-1 cDNA in testes of transgenic mice

Testis-specific lactate dehydrogenase is expressed in somatic tissues of plateau pikas

LDH-C₄ is a lactate dehydrogenase that catalyzes the interconversion of pyruvate with lactate. In mammals the, Ldh-c gene was originally thought to be expressed only in testis and spermatozoa. Plateau pika (Ochotona curzoniae), belonging to the genus Ochotona of the Ochotonidea family, is a hypoxia tolerant mammal living at 3000–5000 m above sea levelon the Qinghai-Tibet Plateau. We found that the expression pattern of six LDH isoenzymes in the somatic tissues of female and male plateau pikas to be the same as those in testis and sperm, suggesting that LDH-C₄ was expressed in somatic tissues of plateau pika. Here we report the detection of LDHC in the somatic tissues of plateau pika using RT-PCR, Western blotting and immunohistochemistry. Our results indicate that Ldh-c mRNA is transcribed in the heart, liver, lung, kidney, brain, skeletal muscle and testis. In somatic tissues LDHC was translated in the cytoplasm, while in testis it was expressed in both cytoplasm and mitochondria. The third band from cathode to anode in LDH isoenzymes was identified as LDH-C₄. The finding that Ldh-c is expressed in both somatic tissues and testis of plateau pika provides important implications for more in-depth research into the Ldh-c function in mammals.

Inactivation of CUG-BP1/CELF1 causes growth, viability, and spermatogenesis defects in mice

CUG-BP1/CELF1 is a multifunctional RNA-binding protein involved in the regulation of alternative splicing and translation. To elucidate its role in mammalian development, we produced mice in which the Cugbp1 gene was inactivated by homologous recombination. These Cugbp1(-/-) mice were viable, although a significant portion of them did not survive after the first few days of life. They displayed growth retardation, and most Cugbp1(-/-) males and females exhibited impaired fertility. Male infertility was more thoroughly investigated. Histological examination of testes from Cugbp1(-/-) males showed an arrest of spermatogenesis that occurred at step 7 of spermiogenesis, before spermatid elongation begins, and an increased apoptosis. A quantitative reverse transcriptase PCR analysis showed a decrease of all the germ cell markers tested but not of Sertoli and Leydig markers, suggesting a general decrease in germ cell number. In wild-type testes, CUG-BP1 is expressed in germ cells from spermatogonia to round spermatids and also in Sertoli and Leydig cells. These findings demonstrate that CUG-BP1 is required for completion of spermatogenesis.

Genomic and Expression Profiling of Human Spermatocytic Seminomas: Primary Spermatocyte as Tumorigenic Precursor and DMRT1 as Candidate Chromosome 9 Gene

Spermatocytic seminomas are solid tumors found solely in the testis of predominantly elderly individuals. We investigated these tumors using a genome-wide analysis for structural and numerical chromosomal changes through conventional karyotyping, spectral karyotyping, and array comparative genomic hybridization using a 32 K genomic tiling-path resolution BAC platform (confirmed by in situ hybridization). Our panel of five spermatocytic seminomas showed a specific pattern of chromosomal imbalances, mainly numerical in nature (range, 3-24 per tumor). Gain of chromosome 9 was the only consistent anomaly, which in one case also involved amplification of the 9p21.3-pter region. Parallel chromosome level expression profiling as well as microarray expression analyses (Affymetrix U133 plus 2.0) was also done. Unsupervised cluster analysis showed that a profile containing transcriptional data on 373 genes (difference of > or = 3.0-fold) is suitable for distinguishing these tumors from seminomas/dysgerminomas. The diagnostic markers SSX2-4 and POU5F1 (OCT3/OCT4), previously identified by us, were among the top discriminatory genes, thereby validating the experimental set-up. In addition, novel discriminatory markers suitable for diagnostic purposes were identified, including Deleted in Azospermia (DAZ). Although the seminomas/dysgerminomas were characterized by expression of stem cell-specific genes (e.g., POU5F1, PROM1/CD133, and ZFP42), spermatocytic seminomas expressed multiple cancer testis antigens, including TSP50 and CTCFL (BORIS), as well as genes known to be expressed specifically during prophase meiosis I (TCFL5, CLGN, and LDHc). This is consistent with different cells of origin, the primordial germ cell and primary spermatocyte, respectively. Based on the region of amplification defined on 9p and the associated expression plus confirmatory immunohistochemistry, DMRT1 (a male-specific transcriptional regulator) was identified as a likely candidate gene for involvement in the development of spermatocytic seminomas.

Lessons from knockout and transgenic mice for infertility in men

This review concentrates on the clear cases where knocking out a gene in mice has caused male infertility and thus comes near to proving that the gene plays a role in the development of sperm. Knockout mice have been created with primary defects at every stage of spermatogenesis thus creating a framework for decoding the genetic hierarchy that causes male germ cell differentiation. As well as defining essential genes in vivo experiments have defined promoter and untranslated sequences responsible for the expression of proteins at all the spermatogenic stages. In conclusion knockout mice remain the ultimate test of spermatogenic hypotheses as well as providing detailed information about this complex process.

Transgenic mice demonstrate a testis-specific promoter for lactate dehydrogenase, LDHC

The mammalian genome encodes a family of lactate dehydrogenase (LDH) isozymes. Two of these, ldha and ldhb, are expressed ubiquitously. The ldhc gene is active only in the germinal epithelium during spermatogenesis. In our analysis of ldhc gene regulation, we found that a 60-base pair promoter sequence was sufficient for testis-specific expression in an in vitro transcription assay. To confirm these findings, a genomic fragment containing 100 base pairs overlapping the transcription start site was isolated and linked to the Escherichia coli lacZ gene. We report that this genomic fragment drives testis-specific expression in transgenic mice. We conclude that transcription of the transgene and possibly of the endogenous ldhc gene is restricted to leptotene/pachytene primary spermatocytes.