THE LETHAL MUTATION OF THE MOUSE WASTED (WST) IS A DELETION THAT ABOLISHES EXPRESSION OF A TISSUE-SPECIFIC ISOFORM OF TRANSLATION ELONGATION-FACTOR 1-ALPHA, ENCODED BY THE EEFLA2 GENE

We have identified the mutation responsible for the autosomal recessiv e wasted (,wst) mutation of the mouse. Wasted mice are characterized b y wasting and neurological and immunological abnormalities starting at 21 days after birth; they die by 28 days. A deletion of 15.8 kb in wa sted mice abolishes expression of a gene called Eefla2, encoding a pro tein that is 92% identical at the amino acid level to the translation elongation factor EF1 alpha (locus Eef1a), We have found no evidence f or the involvement of another gene in this deletion. Expression of Eef 1a2 is reciprocal with that of Eef1a, Expression of Eef1a2 takes over from Eef1a in heart and muscle at precisely the time at which the wast ed phenotype becomes manifest, These data suggest that there are tissu e-specific forms of the translation elongation apparatus essential for postnatal survival in the mouse.