SWINE CYTOSOLIC MALIC ENZYME - CDNA CLONING, SEQUENCING, AND LOCALIZATION

A highly significant genetic association has been found between some a lleles of the swine Major Histocompatibility Complex SLA (Swine Leukoc yte Antigen genetic complex) and the cytosolic malic enzymatic activit y level in muscles. The aim of this study was to find out whether this genetic association was due to a close linkage of the SLA region and the gene coding for the enzyme. Since no swine cytosolic malic enzyme sequence (ME1) was available, we isolated several overlapping fragment s that spanned the almost entire malic enzyme transcript both by scree ning of a swine cDNA library and by RT-PCR. The results indicated the existence of two transcripts of 2.0 and 3.1 kb, which probably corresp ond to two alternative forms of one gene. The sequence of the transcri pt was highly similar to the other published mammalian cytosolic NADP( +)-dependent malic enzyme cDNA, especially within the four functional domains. Two major bands at 3.7 and 2.4 kb were detected on Northern b lots containing the RNA from 25 tissues from fetuses and adult pigs. A high expression level was found in the adrenal gland, muscle, liver, and peripheral nerves. The analysis of malic enzyme RFLPs in five SLA informative families revealed an independent segregation of the ME1 ge ne from the SLA region. In situ hybridization results localized the cy tosolic malic enzyme on the swine Chromosome (Chr) 1p1.2, except that the association between SLA and the malic enzyme activity level was du e to a physical genetic linkage. Thus, the mechanisms underlying this association remain to be elucidated.