Gene expression profiles of Wnt4 high and Wnt4 low populations of murine islets at postnatal day 1 (P1).

To find the differences between β cells expressing Wnt4 and those that do not express it (or express it at low levels) at neonatal stage, murine islets at postnatal day 1 (P1) were collected. Based on a reporter expressing Cre recombinase from the Wnt4 locus, we observed that Wnt4 expression starts in a small subset of β cells at embryonic day (E) 18.5. At neonatal stages, around 50% of β cells express Wnt4 at P0 and most of cells express it by P5. We collected Wnt4 high and Wnt4 low islet cells by FACS and compared their gene expression profile. Wnt4 high islet cell population showed a significant increase of β-cell maturation and function related genes, including transcription factors such as Pdx1 and Nkx6.1, insulin 2, glucokinase (Gck), and the glucose transporter Slc2a2. On the contrary, Wnt4 low islet cell population showed significant increasing of proliferation markers such as Pcna, Mki67 and the positive cell cycle regulators Ccnd1, Ccnd3, Ccna2, Cdk1, Cdk2 and Cdk6. Taken together, these results show that Wnt4 expression is higher in more mature but less proliferative β cells. To follow the Wnt4 expression in β cells, Wnt4eGFPCre (Wnt4 tm2(EGFP/cre)Svo) mice were crossed with mTmG (Gt(ROSA)26Sor tm4(ACTB−tdTomato,−EGFP)Luo) mice to generate Wnt4eGFPCre;mTmG mice. The islets were collected at P1. The islets from 3-4 pups were pooled together into 1 sample. Wnt4 high and low islet cells were sorted by FACS based on mGFP expression.