Mutations in the human ALMS1 gene are responsible for Alström syndrome, a disorder in which key metabolic and endocrinological features include childhood-onset obesity, metabolic syndrome, and diabetes, as well as infertility. ALMS1 localizes to the basal bodies of cilia and plays a role in intracellular trafficking, but the biological functions of ALMS1 and how these relate to the pathogenesis of obesity, diabetes, and infertility remain unclear. Here we describe a new mouse model of Alström syndrome, fat aussie, caused by a spontaneous mutation in the Alms1 gene. Fat aussie (Alms1 foz/foz) mice are of normal weight when young but, by 120 d of age, they become obese and hyperinsulinemic. Diabetes develops in Alms1 foz/foz mice accompanied by pancreatic islet hyperplasia and islet cysts. Female mice are fertile before the onset of obesity and metabolic syndrome; however, male fat aussie mice are sterile due to a progressive germ cell loss followed by an almost complete block of development at the round-to-elongating spermatid stage of spermatogenesis. In conclusion, Alms1 foz/foz mouse is a new animal model in which to study the pathogenesis of the metabolic and fertility defects of Alström syndrome, including the role of ALMS1 in appetite regulation, pathogenesis of the metabolic syndrome, pancreatic islet physiology, and spermatogenesis.

Sox8 encodes a high-mobility group transcription factor that is widely expressed during development. Sox8, -9 and -10 form group E of the Sox gene family which has been implicated in several human developmental disorders. In contrast to other SoxE genes, the role of Sox8 is unclear and Sox8 mouse mutants reportedly showed only idiopathic weight loss and reduced bone density. The careful analysis of our Sox8 null mice, however, revealed a progressive male infertility phenotype. Sox8 null males only sporadically produced litters of reduced size at young ages. We have shown that SOX8 protein is a product of adult Sertoli cells and its elimination results in an age-dependent deregulation of spermatogenesis, characterized by sloughing of spermatocytes and round spermatids, spermiation failure and a progressive disorganization of the spermatogenic cycle, which resulted in the inappropriate placement and juxtaposition of germ cell types within the epithelium. Those sperm that did enter the epididymides displayed abnormal motility. These data show that SOX8 is a critical regulator of adult Sertoli cell function and is required for both its cytoarchitectural and paracrine interactions with germ cells.