SEGREGATION ANALYSIS REVEALS TIGHT GENETIC-LINKAGE BETWEEN THE SPONTANEOUSLY ARISING NEURAL-TUBE DEFECT GENE SPLOTCH (SP) AND PAX-3 IN AN INTRASPECIFIC MOUSE BACKCROSS

Concurrent research has recently characterized Sp2H, a radiation induced mutation at the splotch (Sp) locus, and found alterations in the murine paired box gene, Pax-3, in homozygous Sp2H DNA. It was proposed that Sp and Pax-3 are the same gene. This report presents additional genetic evidence in support of this finding through linkage studies. Southern blot analysis of genomic DNAs from a panel of 125 intraspecific [(Sp/+ x CBA/J)F1 - Sp x CBA/J] backcross mice reveals no crossover between Pax-3 and the spontaneously occurring splotch allele, Sp. This positions Pax-3 within 2.9 cM of the Sp locus (95% confidence interval) and suggests tight genetic linkage between the two marker genes.