Regional localization of sex-specific Bkm-related sequences on proximal chromosome 17 of mice

Development and fertility in the mouse are known to be influenced by loci mapped to the T/t complex of chromosome 17. Recent evidence suggests that one or more genes near this region may also be associated with sex determination. Washburn and Eicher recently reported partial to complete sex reversal with the Thp deletion on some genetic backgrounds and suggest that this result may be due to a primary sex-determining locus (Tas) that is closely linked to, or a part of, the T locus. Sex-specific, Bkm (banded Krait minor satellite DNA)-related sequences are known to have autosomal as well as heterogametic sex chromosomal copies, but specific regions of autosomal localization have not been described. We now demonstrate the presence of chromosome Y-related DNA sequences on proximal chromosome 17 in Sex-reversed (Sxr) and normal mice using in situ hybridization of mitotic chromosomes with 3H-labelled pCS316 (ref. 4), a probe that shows major hybridization to the proximal portion of the mouse chromosome Y. These data, and those of Washburn and Eicher, argue for a gene(s) related to sex determination or differentiation within the proximal portion of mouse chromosome 17.     

Complete nucleotide sequence of an immunoglobulin VH gene homologue from Caiman, a phylogenetically ancient reptile

Immunoglobulin variable (V) gene regions typify extensive multigenic families in terms of overall size, chromosomal arrangement and presence of large numbers of apparent pseudogenes. A unique mechanism of somatic reorganization involving recombination of VH, D and JH or VL and JL segments accompanies the differentiation of lymphoid cells and together with somatic mutation and other types of recombination accounts for V-region diversity. Although these processes have been well characterized in higher mammals, little is known concerning their origin and diversification during phylogenetic time. Previously, we described the blot-hybridization characteristics of murine VHIII probes with restriction enzyme-digested genomic DNA isolated from several phylogenetically critical species, including Caiman crocodylus, a modern representative of an ancient reptilian subclass. Here we have used a murine probe, S107V, to select homologous clones from a library of Caiman genomic DNA constructed in a lambda bacteriophage. The complete nucleotide sequence of a Caiman gene homologous to the murine VH gene and its adjacent 5' and 3' region is described. Comparison of the sequence with mammalian prototypes shows evidence of considerable organizational and structural homology extending outside the presumed VH-coding region and including elements believed to be involved in somatic recombination. Inferences about the evolution of this multigenic family can now be extended to the level of phylogenetic class.