Rationale. The family of calcium-activated potassium channels consists of four members with varying biological functions and conductances. Besides membrane potential modulation, SK channels have been found to be involved in cardiac pacemaker cell development from ES cells and morphological shaping of neural stem cells. Objective. Distinct SK channel subtype expression in ES cells might elucidate their precise impact during cardiac development. We chose SK channel subtype 4 as a potential candidate influencing embryonic stem cell differentiation. Methods. We generated a doxycycline inducible mouse ES cell line via targeted homologous recombination of a cassette expressing a bicistronic construct encoding SK4 and a fluorophore from the murine HPRT locus. Conclusion. We characterized the mouse ES cell line iSK4-AcGFP. The cassette is readily expressed under the control of doxycycline, and the overexpression of SK4 led to an increase in cardiac and pacemaker cell differentiation thereby serving as a unique tool to characterize the cell biological variances due to specific SK channel overexpression.

Cell-fate decisions and pluripotency are dependent on networks of key transcriptional regulators. Recent reports demonstrated additional functions of pluripotency-associated factors during early lineage commitment. The T-box transcription factor TBX3 has been implicated in regulating embryonic stem cell self-renewal and cardiogenesis. Here, we show that TBX3 is dynamically expressed during specification of the mesendoderm lineages in differentiating embryonic stem cells (ESCs) in vitro and in developing mouse and Xenopus embryos in vivo. Forced TBX3 expression in ESCs promotes mesendoderm specification by directly activating key lineage specification factors and indirectly by enhancing paracrine Nodal/Smad2 signaling. TBX3 loss-of-function analyses in the Xenopus underline its requirement for mesendoderm lineage commitment. Moreover, we uncovered a functional redundancy between TBX3 and Tbx2 during Xenopus gastrulation. Taken together, we define further facets of TBX3 actions and map TBX3 as an upstream regulator of the mesendoderm transcriptional program during gastrulation.

Genes involved in distinct diabetes types suggest shared disease mechanisms. Here we show that One Cut Homeobox 1 (ONECUT1) mutations cause monogenic recessive syndromic diabetes in two unrelated patients, characterized by intrauterine growth retardation, pancreas hypoplasia and gallbladder agenesis/hypoplasia, and early-onset diabetes in heterozygous relatives. Heterozygous carriers of rare coding variants of ONECUT1 define a distinctive subgroup of diabetic patients with early-onset, nonautoimmune diabetes, who respond well to diabetes treatment. In addition, common regulatory ONECUT1 variants are associated with multifactorial type 2 diabetes. Directed differentiation of human pluripotent stem cells revealed that loss of ONECUT1 impairs pancreatic progenitor formation and a subsequent endocrine program. Loss of ONECUT1 altered transcription factor binding and enhancer activity and NKX2.2/NKX6.1 expression in pancreatic progenitor cells. Collectively, we demonstrate that ONECUT1 controls a transcriptional and epigenetic machinery regulating endocrine development, involved in a spectrum of diabetes, encompassing monogenic (recessive and dominant) as well as multifactorial inheritance. Our findings highlight the broad contribution of ONECUT1 in diabetes pathogenesis, marking an important step toward precision diabetes medicine.