Sperm 1: a POU-domain gene transiently expressed immediately before meiosis I in the male germ cell.

Members of the POU-homeodomain gene family encode transcriptional regulatory molecules that play important roles in terminal differentiation of many organ systems. Sperm-1 (Sprm-1) is a POU domain factor that is exclusively expressed in the differentiating male germ cell. We show here that the Sprm-1 protein is expressed in the haploid spermatid and that 129͞Sv Sprm-1(؊͞؊) mice are subfertile when compared with wild-type or heterozygous littermates yet exhibit normal testicular morphology and produce normal numbers of mobile spermatozoa. Our data suggest that the Sprm-1 protein plays a discrete regulatory function in the haploid spermatid, which is required for the optimal function, but not the terminal differentiation, of the male germ cell.It is estimated that 15% of all married couples in the United States experience fertility problems, of which half of the cases are thought to result from infertility in the male (1). The diagnosis in 40-60% of cases of male infertility is idiopathic infertility, which, as the name implies, has an enigmatic etiology. Many of these males exhibit oligozoospermia, which is characterized by a reduction of sperm concentration in the ejaculate from greater than 50 million per ml to less than 10-20 million sperm per ml. But many still exhibit relatively normal concentrations of mobile spermatozoa.Spermatogenesis is a complex cellular differentiation process whereby a single diploid cell gives rise to thousands of highly specialized haploid spermatozoa (2, 3). The stem cells of the testis arise by invasion of the embryonic genital ridges by migrating primordial germ cells. These stem cells, known as type A spermatogonia, proliferate either to self-renew or to generate type B spermatogonia. Puberty is initiated by signals from the hypothalamic-pituitary axis, which direct the progression of type B spermatogonia to primary spermatocytes. The final cellular division in this process is the meiotic reduction of secondary spermatocytes that generates haploid spermatids. These spermatids exist as a syncytial bundle that undergoes dramatic morphological and genetic changes to produce functional, mobile spermatozoa in a process known as spermiogenesis. During this entire differentiation process germ cells maintain intimate contact with the supporting Sertoli cells, which, in response to hormonal stimuli from the pituitary and Leydig cells, provide the appropriate environment for germ cell maturation.It was thought previously that a surge of RNA synthesis immediately before the meiotic reduction, along with RNA storage and translational regulation, provided sufficient resources during spermiogenesis to obviate the need for de novo haploid gene transcription (4). However, advances in cloning strategies have led to the identification of many genes that are not transcribed until after the meiotic reduction (5). Indeed, it has been shown recently that many haploid-expressed genes are regulated by the cyclic AMP-responsive element modulator protein CREM (6, 7).Results of the analyses of mic...

Section: It Is Estimated That 15% Of All Married Couples In the Unitedmentioning

confidence: 54%

Reduced fertility in mice deficient for the POU protein sperm-1

Pearse

Drolet

Kalla

et al. 1997

“…3E). Hlf3 (encoding histone H1t) is expressed in midto late-pachytene spermatocytes (22) and Sprm1 is transiently expressed from late-pachytene to diprotene (23). The transcripts from these genes were present in Cst Ϫ/Ϫ testes at the same levels as in the wild type.…”

Section: Resultsmentioning

confidence: 96%

Paranodal junction formation and spermatogenesis require sulfoglycolipids

Honke

Hirahara

Dupree

et al. 2002

310

299

Mammalian sulfoglycolipids comprise two major members, sulfatide (HSO3-3-galactosylceramide) and seminolipid (HSO3-3-monogalactosylalkylacylglycerol). Sulfatide is a major lipid component of the myelin sheath and serves as the epitope for the well known oligodendrocyte-marker antibody O4. Seminolipid is synthesized in spermatocytes and maintained in the subsequent germ cell stages. Both sulfoglycolipids can be synthesized in vitro by using the isolated cerebroside sulfotransferase. To investigate the physiological role of sulfoglycolipids and to determine whether sulfatide and seminolipid are biosynthesized in vivo by a single sulfotransferase, Cst-null mice were generated by gene targeting. Cst ؊/؊ mice lacked sulfatide in brain and seminolipid in testis, proving that a single gene copy is responsible for their biosynthesis. Cst ؊/؊ mice were born healthy, but began to display hindlimb weakness by 6 weeks of age and subsequently showed a pronounced tremor and progressive ataxia. Although compact myelin was preserved, Cst ؊/؊ mice displayed abnormalities in paranodal junctions. On the other hand, Cst ؊/؊ males were sterile because of a block in spermatogenesis before the first meiotic division, whereas females were able to breed. These data show a critical role for sulfoglycolipids in myelin function and spermatogenesis.

“…The purified GST-GCM protein was then used in a binding site selection assay, in which the GST-GCM protein was incubated with a pool of oligonucleotides that exhibited randomized sequence at 8 bp in the center (15). GST-GCM bound to such an oligonucleotide (see Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Protein-bound template was identified by elelctrophoretic mobility shift analysis and amplified by PCR in 34 cycles with 5Ј-GGATCCATTCCTAAG-3Ј and 5Ј-AGATCTGATCTGAGC-3Ј as primers. Throughout all six rounds of selection conditions were as previously described for the binding site selection of Sprm-1 (15).…”

Section: Methodsmentioning

confidence: 99%

The regulator of early gliogenesis glial cells missing is a transcription factor with a novel type of DNA-binding domain

Schreiber

Sock

Wegner

1997

111

Absence or presence of glial cells missing (GCM) in cells of the developing nervous system of Drosophila decides over their future fate as neurons or glia with only those cells turning into glia that express GCM. To understand how GCM exerts its function we performed a detailed structurefunction analysis. Using fusions between the DNA binding domain of the yeast GAL4 protein and GCM, we detected a transactivation function within the C-terminal part of GCM. In addition to this transactivation domain we mapped a sequence-specific DNA-binding domain within the N-terminal part of the GCM protein in close proximity to a bipartite nuclear localization signal. Binding site selection assays determined the motif 5 -AT(G͞A)CGGGT-3 as the preferred binding site for GCM. Both the lack of homology to known proteins and the novel DNA binding specificity indicate that GCM contained a new type of DNA-binding domain. In transiently transfected cells, GCM also activated transcription from promoters consisting of the newly identified GCMbinding site and a TATA box. Thus, GCM is a novel type of transcription factor involved in early gliogenesis.