We cloned a testis-specific cDNA from mice that encodes a histone H1-like, haploid germ cell-specific nuclear protein designated HANP1/H1T2. The HANP1/H1T2 protein was specifically localized to the nuclei of murine spermatids during differentiation steps 5 to 13 but not to the nuclei of mature sperm. HANP1/H1T2 contains an arginine-serine-rich domain and an ATP/GTP binding site, and it binds to DNA, ATP, and protamine. To investigate the physiological role of HANP1/H1T2, we generated Hanp1/H1T2-disrupted mutant mice. Homozygous Hanp1/H1T2 mutant males were infertile, but females were fertile. Although a substantial number of sperm were recovered from the epididymides, their shape and function were abnormal. During sperm morphogenesis, the formation of nuclei was disturbed and protamine-1 and -2 were only weakly detectable in the nuclei. The chromatin packaging was aberrant, as demonstrated by electron microscopy and biochemical analysis. The mutant sperm exhibited deficient motility and were not competent to fertilize eggs under in vitro fertilization conditions; however, they were capable of fertilizing eggs via intracytoplasmic sperm injection that resulted in the birth of healthy progeny. Thus, we found that HANP1/H1T2 is essential for nuclear formation in functional spermatozoa and is specifically involved in the replacement of histones with protamines during spermiogenesis. At the time of submission of the manuscript, we found an independent publication by The complex process of spermatogenesis includes three major events: proliferation and differentiation of the spermatogonia, meiotic prophase in the spermatocytes, and drastic morphological changes during differentiation from the haploid round spermatids to the mature sperm (24). These events begin after birth, and approximately 35 days are required for the development of mature sperm in the mouse. The differentiation of the haploid germ cells (spermiogenesis) begins at 17 days of age in the mouse. Spermiogenesis involves diverse and complex processes, such as packaging and remodeling of the haploid germ cell nucleus, rearrangement of mitochondria, development of the flagellum, and formation of the acrosome. During this phase, the composition of the chromatin is altered dramatically (29). The changes in the nuclear proteins occur in association with the displacement of general nucleohistones by transition proteins (TNP) and other proteins, including a number of testis-specific histones and nonhistone chromosomal proteins (3,12,13,17,31) that are subsequently replaced with protamines to form nucleoprotamines (2, 20). The transition from histones to protamines in the chromatin of the haploid germ cells is accompanied by epigenetic changes (19) and the specific formation of nuclei in the sperm (25); these changes are associated with chromosome condensation and the shaping of the nucleus. Recently, mice with null mutations in TNP1 or TNP2 were found to be subfertile (32, 33), and mice with null mutations in both TNP1 and TNP2 were infertile (34). The nuclei of...

We report the isolation of 153 mouse genes whose expression is dramatically up-regulated during spermiogenesis. We used a novel variation of the subtractive hybridization technique called stepwise subtraction, wherein the subtraction process is systematically repeated in a stepwise manner. We named the genes thus identified as TISP genes (transcript induced in spermiogenesis). The transcription of 80 of these TISP genes is almost completely specific to the testis. This transcription is abruptly turned on after 17 days of age, when the mice enter puberty and spermiogenesis is initiated. Considering that the most advanced cells present at these stages of spermatogenesis are the spermatids, it is likely that we could isolate most of the spermatid-specific genes. DNA sequencing revealed that about half the TISP genes are novel and uncharacterized genes, confirming the utility of the stepwise subtraction approach for gene discovery.

Background: Polyamines are known to play important roles in the proliferation and differentiation of many types of cells. However, in the testis, where polyamines such as spermidine and spermine exist in high concentrations, their roles still remains to be elucidated.

We have isolated a cDNA clone encoding a mouse haploid germ cell-specific protein from a subtracted cDNA library. Sequence analysis of the cDNA revealed high homology with pig and human heart succinyl CoA:3-oxo acid CoA transferase (EC 2.8.3.5), which is a key enzyme for energy metabolism of ketone bodies. The deduced protein consists of 520 amino acid residues, including glutamate 344, known to be the catalytic residue in the active site of pig heart CoA transferase and the expected mitochondrial targeting sequence enriched with Arg, Leu, and Ser in the N-terminal region. Thus, we termed this gene scot-t (testis-specific succinyl CoA:3-oxo acid CoA transferase). Northern blot analysis, in situ hybridization, and Western blot analysis demonstrated a unique expression pattern of the mRNA with rapid translation exclusively in late spermatids. The scot-t protein was detected first in elongated spermatids at step 8 or 9 as faint signals and gradually accumulated during spermiogenesis. It was also detected in the midpiece of spermatozoa by immunohistochemistry. The results suggest that the scot-t protein plays important roles in the energy metabolism of spermatozoa.

A fusion gene encoding ribonuclease T 1 -EGFP (rntAegfp) was constructed and expressed to use it as a tool for studies on the secretory pathway in Aspergillus oryzae. The successful secretion of the intact RntA-EGFP fusion protein was detected by ‰uorescence measurement and Western analysis. With use of the RntA-EGFP system, we were able to see high ‰uorescence at hyphal tips and observe concentrated ‰uorescence at septa in basal cells during growth at optimal conditions. Cold or heat shock during growth caused the accumulation of EGFP ‰uorescence in vacuoles.