Maintains stem cell niche architecture in the testes. Activates an extracellular integrin beta-PS pathway which regulates DE-cadherin (shg) levels in somatic hub cells, and is essential for maintaining the number of germline stem cells and the structure and localization of hub cells. Secreted by somatic cells of the testes. Detected at the cell borders between the hub and germline stem cells, and between the germ and cyst stem cells. In the testes, detected at low levels in somatic hub cells, cyst stem cells and the apical tip (at protein level). Levels in the testes decrease with age (at protein level). Expressed at low levels in hub cells, cyst stem cells and germline stem cells, and at high levels in spermatocytes and cyst cells. Males are sterile and display an age-dependent decrease in testes size resulting from a gradual loss in somatic hub cell structure and a decrease in the number of germline stem cells. Hub cells frequently do not localize to the apical tip and are instead present throughout the testes. The number of hub cells is not affected. Reduced DE-cadherin levels in the hub cells. Absence of integrin clustering and decreased focal adhesion kinase (FAK) phosphorylation at the hub/cyst stem cell interface. The name 'shriveled' derives from the shrinking testes phenotype of mutants.