Onecut transcription factors act upstream of Isl1 to regulate spinal motoneuron diversification

Abstract

SUMMARYDuring development, spinal motoneurons (MNs) diversify into a variety of subtypes that are specifically dedicated to the motor control of particular sets of skeletal muscles or visceral organs. MN diversification depends on the coordinated action of several transcriptional regulators including the LIM-HD factor Isl1, which is crucial for MN survival and fate determination. However, how these regulators cooperate to establish each MN subtype remains poorly understood. Here, using phenotypic analyses of single or compound mutant mouse embryos combined with gain-of-function experiments in chick embryonic spinal cord, we demonstrate that the transcriptional activators of the Onecut family critically regulate MN subtype diversification during spinal cord development. We provide evidence that Onecut factors directly stimulate Isl1 expression in specific MN subtypes and are therefore required to maintain Isl1 production at the time of MN diversification. In the absence of Onecut factors, we observed major alterations in MN fate decision characterized by the conversion of somatic to visceral MNs at the thoracic levels of the spinal cord and of medial to lateral MNs in the motor columns that innervate the limbs. Furthermore, we identify Sip1 (Zeb2) as a novel developmental regulator of visceral MN differentiation. Taken together, these data elucidate a comprehensive model wherein Onecut factors control multiple aspects of MN subtype diversification. They also shed light on the late roles of Isl1 in MN fate decision.

The miR-17/106–p38 axis is a key regulator of the neurogenic-to-gliogenic transition in developing neural stem/progenitor cells

“…2 A and B). In support of these findings, a recent study demonstrated that Onecut factors directly regulate Isl-1 expression and maintain Isl-1 production during motor neuron diversification (9). These results suggest that the neurogenic-togliogenic transition in NSPCs, and at least a part of neuron-subtype specification, are independently regulated downstream of Coup-tfs.…”

Onecut1 and Onecut2 redundantly regulate early retinal cell fates during development

“…This conclusion is further supported by the overlap of genes affected in the retinas of single-knockouts, and by the fact that although a larger number of genes demonstrated significant changes of expression in DKO retinas, most of these genes also showed the same direction of changes in the single-knockout retinas. The severity of retinal phenotypes in the three different mutants correlated well with the levels of expression of the two factors (15) also function redundantly in the developing motor neurons in the spinal cord (12). It is likely that the two factors regulate downstream genes in a similar fashion in other developing tissues.…”

“…The members of the "onecut" family of transcription factors play diverse developmental roles (8)(9)(10)(11)(12). In the mouse, three onecut factors, Onecut1 (Oc1), Onecut2 (Oc2), and Onecut3 (Oc3), with essentially identical DNA-binding domains exist (13).…”

The combination of limb-bud removal and in ovo electroporation techniques: A new powerful method to study gene function in motoneurons undergoing lesion-induced cell death

“…By electroporation it is possible to induce the expression of specific genes on dissociated primary cell cultures (in vitro) (Zeitelhofer et al, 2007), organotypic cultures (ex vivo) (Pakan and McDermott, 2014) or in living organisms (in utero or in ovo, when treating mammalian embryos in the uterus or animals developing in egg, respectively) (Bony et al, 2013;Odani et al, 2008). Previous studies have explored the role of many proteins involved in MNs fundamental cellular process, such as axon pathfinding (Winning and Krull, 2011), differentiation (Roy et al, 2012), and survival (Choi et al, 2006(Choi et al, ,2013 employing IOE to overexpress the probe genes.…”