Mouse primordial germ cells lacking beta 1 integrins enter the germline but fail to migrate normally to the gonads

Primordial germ cells are the founder cells of the gametes, They are set as ide at the initial stages of gastrulation in mammals, become embedded in th e hind-gut endoderm, then actively migrate to the sites of gonad formation. The molecular basis of this migration is poorly understood. Here we sought to determine if members of the integrin family of cell surface receptors a re required for primordial germ cell migration, as integrins have been impl icated in the migration of several other motile cell types, We have establi shed a line of mice which express green fluorescent protein in germline cel ls that has enabled us to efficiently purify primordial germ cells at diffe rent stages by flow cytometry. We have catalogued the spectrum of integrin subunit expression by primordial germ cells during and after migration, usi ng flow cytometry, immunocytochemistry and RT-PCR, Through analysis of inte grin beta 1(-/-)-->wild-type chimeras, we show that embryonic cells lacking beta 1 integrins can enter the germline. However, integrin beta 1(-/-) pri mordial germ cells do not colonize the gonad efficiently. Embryos with targ eted deletion of integrin subunit alpha 3, alpha 6, or alpha V show no majo r defects in primordial germ cell migration, These results demonstrate a ro le for beta 1-containing integrins in the development of the germline, alth ough an equivalent role for or integrin subunit(s) has yet to be establishe d.