TFIID is a general transcription factor required for transcription of most protein-coding genes by RNA polymerase II. TAF7L is an X-linked germ cell-specific paralogue of TAF7, which is a generally expressed component of TFIID. Here, we report the generation of Taf7l mutant mice by homologous recombination in embryonic stem cells by using the Cre-loxP strategy. While spermatogenesis was completed in Taf7l ؊/Y mice, the weight of Taf7l ؊/Y testis decreased and the amount of sperm in the epididymides was sharply reduced. Mutant epididymal sperm exhibited abnormal morphology, including folded tails. Sperm motility was significantly reduced, and Taf7l ؊/Y males were fertile with reduced litter size. Microarray profiling revealed that the abundance of six gene transcripts (including Fscn1) in Taf7l ؊/Y testes decreased more than twofold. In particular, FSCN1 is an F-action-bundling protein and thus may be critical for normal sperm morphology and sperm motility. Although deficiency of Taf7l may be compensated in part by Taf7, Taf7l has apparently evolved new specialized functions in the gene-selective transcription in male germ cell differentiation. Our mouse studies suggest that mutations in the human TAF7L gene might be implicated in X-linked oligozoospermia in men.TFIID, a general transcription factor, plays a central role in transcription initiation of most protein-coding genes by RNA polymerase II. TFIID is a multiprotein complex consisting of TATA-binding protein (TBP) and 12 to 15 TBPassociated factors (TAFs) (20,35). The assembly of TFIID at the promoter region recruits other basal transcription factors and RNA polymerase II (2, 31). TAFs play important roles in transcriptional regulation. Some TAFs directly interact with transcriptional activators and thus serve as coactivators. In addition, interactions between TAFs are critical for promoter recognition and selectivity by RNA polymerase II (17,36).Strikingly, studies of a number of tissue-specific TAFs in Drosophila melanogaster and mouse have identified cell-typespecific transcription programs. In Drosophila melanogaster, five testis-specific homologues of widely expressed TAFs have been reported: Can (homologue of dTAF5), Nht (homologue of dTAF4), Mia (homologue of dTAF6), Sa (homologue of dTAF8), and Rye (homologue of dTAF12) (18,19). Null mutations in can, nht, mia, and sa result in the same male sterile phenotype, and all four genes are required for meiotic cell cycle progression and onset of spermatid differentiation (27). In addition, Rye interacts with Nht, suggesting that these five testis-specific TAFs in Drosophila function in the same transcription regulatory pathway (18). Mechanistically, these TAFs may counteract transcriptional repression by Polycomb group (PcG) proteins in spermatocytes (8). In mice, TAF4B (homologue of TAF4) is highly expressed in the testis and the granulosa cells of the ovary, where it is required for follicular development (14). Testes of TAF4B-deficient males are initially normal but undergo progressive germ cell loss, r...

BackgroundThe 11 human cysteine cathepsins are proteases mainly located in the endolysosomal compartment of all cells and within the exocytosis pathways of some secretory cell types. Cathepsin H (Ctsh) has amino- and endopeptidase activities. In vitro studies have demonstrated Ctsh involvement in the processing and secretion of the pulmonary surfactant protein B (SP-B). Furthermore, Ctsh is highly expressed in the secretory organelles of alveolar type II pneumocytes where the surfactant proteins are processed.Methodology/Principal FindingsHence, we generated Ctsh null mice by gene targeting in embryonic stem cells to investigate the role of this protease in surfactant processing in vivo. The targeting construct contains a ß-galactosidase (lacZ) reporter enabling the visualisation of Ctsh expression sites. Ctsh-deficiency was verified by northern blot, western blot, and measurement of the Ctsh aminopeptidase activity. Ctsh −/− mice show no gross phenotype and their development is normal without growth retardation. Broncho-alveolar lavage (BAL) from Ctsh −/− mice contained lower levels of SP-B indicating reduced SP-B secretion. The BAL phospholipid concentration was not different in Ctsh+/+ and Ctsh −/− mice, but measurement of surface tension by pulsating bubble surfactometry revealed an impairment of the tension reducing function of lung surfactant of Ctsh −/− mice.Conclusions/SignificanceWe conclude that cathepsin H is involved in the SP-B production and reduced SP-B levels impair the physical properties of the lung surfactant. However, Ctsh defiency does not reproduce the severe phenotype of SP-B deficient mice. Hence, other proteases of the secretory pathway of type II pneumocytes, i.e. cathepsins C or E, are still able to produce surfactant of sufficient quality in absence of Ctsh.

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