The serendipity alpha gene encodes a membrane-associated protein required for the cellularization of the Drosophila embryo.

The Drosophila serendipity alpha (sry alpha) gene is specifically transcribed at the blastoderm stage, from nuclear cycle 11 to the onset of gastrulation, in all somatic nuclei. This pattern of transcription and a zygotic cellularization defect observed in embryos homozygous for Df(3R)X3F, a deficiency covering the sry locus, suggest that sry alpha plays a role in the cellularization of the syncytial blastoderm embryo. P-element rescue experiments show that one copy of the sry alpha gene rescues the defective cellularization phenotype associated with Df(3R)X3F. Lack of sry alpha activity results in erratic disruptions of the cytoskeleton at the beginning of the interphase of mitotic cycle 14. Multinucleate cells form during plasma membrane invagination. Immunodetection of the sry alpha protein using anti-sry alpha polyclonal antibodies indicates that the 58-kD sry alpha protein accumulates transiently at the blastoderm stage. The sry alpha protein is associated with the invaginating plasma membrane and colocalizes with F-actin. We propose that sry alpha is involved in the localization of membrane furrows within the syncytial blastoderm.