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The HMG box transcription factor Sox9 plays a critical role in progenitor cell expansion during pancreas organogenesis and is required for proper endocrine cell development in the embryo. Based on in vitro studies it has been suggested that Sox9 controls expression of a network of important developmental regulators, including Tcf2/MODY5, Hnf6, and Foxa2, in pancreatic progenitor cells. Here, we sought to: 1) determine whether Sox9 regulates this transcriptional network in vivo and 2) investigate whether reduced Sox9 gene dosage leads to impaired glucose homeostasis in adult mice. Employing two genetic models of temporally-controlled Sox9 inactivation in pancreatic progenitor cells, we demonstrate that contrary to in vitro findings, Sox9 is not required for Tcf2, Hnf6, or Foxa2 expression in vivo. Moreover, our analysis revealed a novel role for Sox9 in maintaining the expression of Pdx1/MODY4, which is an important transcriptional regulator of beta-cell development. We further show that reduced beta-cell mass in Sox9-haploinsufficient mice leads to glucose intolerance during adulthood. Sox9-haploinsufficient mice displayed 50% reduced beta-cell mass at birth, which recovered partially via a compensatory increase in beta-cell proliferation early postnatally. Endocrine islets from mice with reduced Sox9 gene dosage exhibited normal glucose stimulated insulin secretion. Our findings show Sox9 plays an important role in endocrine development by maintaining Ngn3 and Pdx1 expression. Glucose intolerance in Sox9-haploinsufficient mice suggests that mutations in Sox9 could play a role in diabetes in humans.

In this study, we determined the phospholipid FA composition in the mammary gland of the transgenic Fat-1 mouse. This is the first animal model developed that can endogenously synthesize n-3 PUFA. The synthesis of n-3 PUFA is achieved through the expression of the fat-1 transgene encoding for an n-3 desaturase from Caenorhabditis elegans, which utilizes n-6 PUFA as substrate. Wild-type and Fat-1 female mice were terminated at 7 wk of age and the fifth mammary gland was removed. Lipids were extracted and phospholipids were separated by TLC and converted to FAME for analysis by GC. There was no significant change in total saturated, monounsaturated, and PUFA composition. However, there was a significant increase in total n-3 PUFA and a corresponding decrease in n-6 PUFA. The major n-3 PUFA that were enriched included 20:5n-3 and 22:6n-3. The n-6 PUFA that were reduced included 20:4n-6, 22:4n-6, and 22:5n-6. Overall, these findings demonstrate that female Fat-i mice have elevated levels of n-3 PUFA in the mammary gland. Moreover, the n-3 desaturase products are the same n-3 PUFA found in fish oil, which have been shown to have chemoprotective properties against breast cancer. Therefore, this newly developed mouse model may be highly useful for investigating molecular and cellular mechanisms by which n-3 PUFA prevents and inhibits breast cancer growth.

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Delivering genes to and across the brain vasculature efficiently and specifically across species remains a critical challenge for addressing neurological diseases. We have evolved adeno-associated virus (AAV9) capsids into vectors that transduce brain endothelial cells specifically and efficiently following systemic administration in wild-type mice with diverse genetic backgrounds and rats. These AAVs also exhibit superior transduction of the CNS across non-human primates (marmosets and rhesus macaques), and ex vivo human brain slices although the endothelial tropism is not conserved across species. The capsid modifications translate from AAV9 to other serotypes such as AAV1 and AAV-DJ, enabling serotype switching for sequential AAV administration in mice. We demonstrate that the endothelial-specific mouse capsids can be used to genetically engineer the blood-brain barrier by transforming the mouse brain vasculature into a functional biofactory. Vasculature-secreted Hevin (a synaptogenic protein) rescued synaptic deficits in a mouse model.