Structural organization, sequence, and expression of the mouse HEXA gene encoding the alpha subunit of hexosaminidase A.

Genomic clones of the mouse HEXA gene encoding the alpha subunit of lysosomal beta-hexosaminidase A have been isolated, analyzed, and sequenced. The HEXA gene spans approximately 26 kb and consists of 14 exons and 13 introns. The 5' flanking region of the gene has three candidate GC boxes and a number of potential promoter and regulatory elements. Promoter analysis using deletion constructs of 5' flanking sequence fused to the bacterial chloramphenicol acetyltransferase (CAT) gene showed that 150 bp of 5' sequence was sufficient for expression in transfected monkey kidney COS cells. Determination of the sequence of the 5' end of the Hex alpha mRNA by an "anchor-ligation PCR" procedure showed that transcription is initiated from a cluster of sites centered -42, -32, and -21 bp from the first in-frame ATG. Northern blot analysis from 11 different tissues showed over five times the steady-state level of Hex alpha mRNA in testis as compared to that found in three different brain regions; the lowest level (about 1/3 of brain) was found in liver. Comparison of the 5' flanking sequence with that of the human HEXA gene revealed 78% identity within the first 100 bp. These data suggest that the mouse HEXA gene is controlled mainly by sequences located within 150 bp of the 5' flanking region, and we speculate that it may have a role, not only in brain and other tissues, but also in reproductive function in the adult male mouse.