Confirmation of assignment of the human α1-crystallin gene (CRYA1) to chromosome 21 with regional localization to q22.3

The crystallins are highly conserved structural proteins universally found in the eye lens of all vertebrate species. In mammals, three immunologically distinct classes are present, α-, β-, and γ-crystallins, and each class represents a multigene family. The α-crystallin gene family consists of α1-crystallin (CRYA1) and α2-crystallin (CRYA2) genes (previously designated αA-and αB-crystallin, respectively), which show extensive sequence homology. We constructed a synthetic oligonucleotide probe of 25 bases corresponding to a specific region of the human α1-crystallin gene sequence. This 25-mer probe bears little sequence homology to human α2-crystallin gene and does not cross-hybridize to α2-crystallin sequences in Southern blot analysis. Using this unique synthetic probe, we have demonstrated the identity of the α1-crystallin gene in human genomic DNA. In addition, we have also confirmed its chromosomal location on human chromosome 21. Finally, we have regionally localized the gene to q22.3 by using both Southern blot analysis of a panel of cell hybrids containing different parts of human chromosome 21, and in situ hybridization to metaphase chromosomes. The use of synthetic oligonucleotide probes specific for individual genes should be useful in identifying and mapping members of multigene families.