Mapping and cloning recombinant breakpoints demarcating the Hybrid Sterility 6-specific sperm tail assembly defect |
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Authors: | Sadhara A Samant John Fossella Lee M Silver Stephen H Pilder |
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Institution: | (1) Department of Anatomy and Cell Biology, Temple University School of Medicine, 3400 North Broad Street, Philadelphia, Pennsylvania 19140, USA, US;(2) Department of Molecular Biology, Princeton University, Washington Road, Princeton, New Jersey 08540, USA, US |
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Abstract: | Variants of the mouse t complex known as t haplotypes (t) express factors that perturb sperm differentiation, resulting in the non-Mendelian transmission of t from +/t heterozygous males and the sterility of t/t homozygous males. Previous studies of mice carrying heterospecific combinations of the t complex have revealed a 1-cM candidate locus, Hst6, for the distal-most of these factors, Tcd/Tcs2. Males heterozygous for the M. spretus allele of Hst6 and a t haplotype (Hst6
s
/t) are sterile, expressing an abnormality in sperm flagellar curvature (``curlicue') indistinguishable from one exhibited
by sperm from t/t homozygotes. Hst6
s
/Hst6
s
males are also sterile; however, sperm produced by these males are completely immotile owing to the absence of assembled
flagella. Recent studies have shown that the complete presentation of ``curlicue' derives from expression of at least two
factors within the locus, Curlicue a (Ccua) proximally and Curlicue b (Ccub) distally, with a factor affecting sperm-oolemma penetration, Stop1p, mapping between them. In the present report, we have examined expression of the Hst6-specific flagellar assembly phenotype in sperm from mice homozygous for M. spretus–M. m. domesticus recombinant Chr 17 homologs whose breakpoints map within the Hst6 locus. SSLP analysis of these homologs has demonstrated that the flagellar assembly defect maps to less than 0.2 cM between
D17Mit61 and D17Mit135, coincident with Ccua. SSR content analysis of 23 BACs mapping to four contigs within the Hst6 locus has resulted in isolation of proximal and distal recombinant breakpoints circumscribing the flagellar assembly phenotype/Ccua factor. In addition, we have provided increased high-resolution mapping of the Stop1p and Ccub factors. These new data enhance our ability to isolate and characterize candidates for Tcd/Tcs2.
Received: 12 August 1998 / Accepted: 1 October 1998 |
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