Ankyrin Repeat Domain Protein 5 (ANKRD5)

Of the 16 known genes mapping to the male-specific locus for total IgE on chromosome 20p12, two were of particular interest:jagged 1 precursor (JAG1) and ankyrin repeat domain protein 5 (ANKRD5). JAG1, an important growth factor implicated in hematopoietic stem cell self-renewal, is within 0.5 Mb of the STR demonstrating maximal linkage to total IgE. JAG1 is expressed in mature B-cells, and is a principal ligand for the NOTCH1 receptor, which (in conjunction with Delta-1) has been implicated in lymphocyte precursor stem cell differentiation into T- or B-cell lineages. ANKRD5 contains eight ankyrin repeat domains and a calcium binding EF-hand domain, and is expressed in both the bone marrow and spleen. STR strongly linked to total IgE—resides within the 30 untranslated region of ANKRD5.