Genetics, Vol 120, 545-550, Copyright © 1988

INVESTIGATIONS

The Antimorphic Nature of the T(c) Allele at the Mouse T Locus

A. MacMurray and H. S. Shin
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

The T locus on mouse chromosome 17 is haploid-insufficient: deletion/+ heterozygous mice have a short tail. One exceptional allele, T(c), produces a tailless phenotype in heterozygous mice. Thus, T(c) has a more severe phenotype than that of a deletion allele, suggesting either that T(c) is further deleted for a neighboring locus, resulting in the additional phenotype, or that T(c) is a gain-of-function mutation. We have shown that T(c) is not deleted for the D17Leh119 and D17RP17 loci flanking T, which are deleted in some T alleles. Thus, the severity of the T(c) phenotype is not due to the deletion of an adjacent locus. We have also examined the genetic nature of the T(c) allele by placing it in trans with a T-locus duplication, t(wLub2), which has previously been independently confirmed at the molecular level to have a duplication in the chromosomal region including the T locus. We have shown that T(c) is partially complemented by t(wLub2), unlike a null allele (deletion) which was previously shown to be fully complemented by t(wLub2). These results indicate that T(c) behaves genetically as an antimorph, exerting its effect by antagonizing the function of a wild-type allele at the T locus. The apparent correlation between the gene dosage at the T locus and the length of the body axis is discussed.

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