International Mammalian Genome Society

logo18th International Mouse Genome Conference

17-22 October 2004, Seattle, USA


POSTER 62 - THE MOUSE JUVENILE SPERMATOGONIAL DEPLETION (JSD) PHENOTYPE IS DUE TO A MUTATION IN MUTP14B, A MEMBER OF THE SNORNP COMPLEX

Rohozinski J 1, Bishop CE  2

1 Baylor College of Medicine, Dept. Obstetrics & Gynecology, Houston, United States, 2 Baylor College of Medicine, Dept. Molecular & Human Genetics, Houston, United States

The recessive juvenile spermatogonial depletion (jsd) mutation results in a single wave of spermatogenesis, followed by failure of type A spermatogonia to differentiate, resulting in adult male sterility. We have identified a jsd specific, rearrangement in the mouse homologue of the S. cerevisiae gene Utp14, provisionally termed mUtp14b. Confirmation that mUtp14b underlies the  jsd phenotype was obtained by transgenic BAC rescue. We also identified a homologous gene on the MMUX (mUtp14a) which is the strict homologue of the yeast gene, from which the intronless mUtp14b has been derived by retrotransposition. Expression analysis showed that mUtp14b is predominantly  expressed in the germ line of the testis from zygotene through round spermatids whereas mUtp14a, although well expressed in all  somatic tissues, could only be detected in the germ line in round spermatids. In yeast, depletion of the UTP proteins impedes production of 18S rRNA, leading to cell death. We propose that the retroposed autosomal copy, mUtp14b, having  acquired a testis specific expression pattern, could have provided a mechanism for increasing the efficiency and/or numbers of germ cells produced, by meeting the need for more 18S rRNA and protein. Such a mechanism would be of obvious reproductive advantage and be strongly selected for in evolution. Consistent with this hypothesis is the finding of a similar X-autosome retroposition of UTP14 in human which appears to have arisen independently of that in rodents. In jsd homozygotes, which lack a functional copy of Utp14b, insufficient production of rRNA quickly leads to a cessation of spermatogenesis.

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