Mutations within the Ery1 transcriptional unit are associated with juvenile lethality, neuromuscular tremors and germ cell defects in jdf2 mutant mice and pigmentation abnormalities in p [superscript x] and p [supercript m] alleles

This dissertation describes the cloning of a large gene, called Ery1, and presents evidence to link mutations in this gene to pleiotropic affects associated with certain deletions in the mouse pink-eyed dilution (p) region of mouse chromosome 7. This complex phenotype, called the 'pink-eye effect' includes reduced-life span, severe runting, neurologic symptoms, and a characteristic sperm cell defect. The identification of several EtNU-induced alleles that fail to complement defects associated with p^6H, a p deletion allele historically associated with the 'pink eye effect', has indicated that this complex phenotype is due to mutations in a single locus, termed juvenile development and fertility locus 2 (jdf2).

Here we report the construction of a physical map of the jdf2 region and cloning of a highly conserved gene, called Ery1 (En d Repeat familY 1). Alterations of genomic structure and/or expression of Ery1 were detected in seventeen of eighteen jdf2 alleles examined, providing strong evidence that defective Ery1 function is the cause of the pink-eye/jdf2 effect in mutant mice. In the course of these studies we have also identified rearrangements that permit us to predict the location of sequences associated with intermediate(p^x) and mottled (p^m) p pigmentation defects in several mutant alleles.

In a collaborative effort, we have cloned and sequenced the complete >15 kb Ery1 cDNA sequence. The predicted protein contains five recognized protein motifs including three complete copies of a motif related to RCCl, a protein associated with defects in nuclear transport, structure and cell cycle control. Ery1 also contains a "ZZ"-type zinc finger structure and a HECT domain, the latter of which has been proposed for a role in the ubiquitin intracellular signaling pathway. Ery1 may act as a guanine nucleotide exchange factor (GEE), as documented for p532, a related HECT domain-containing protein. Alternatively, I propose that Ery1’s essential function is in the ubiquitin tagging or degradation pathway, and that the pleiotropic phenotype expressed by jdf2 mutant mice reflects the involvement of this essential gene at a crosspoint between several fundamental cellular processes.