Single-cell transcriptomics reveals the cellular identity of a novel progenitor population crucial for murine neural tube closure

Neural tube closure in vertebrates is achieved through a highly dynamic and coordinated series of morphogenic events involving neuroepithelium, surface ectoderm, and neural plate border. Failure of this process in the caudal region causes spina bifida. Grainyhead-like 3 (GRHL3) is an indispensable transcription factor for neural tube closure as constitutive inactivation of the <i>Grhl3</i> gene in mice leads to fully penetrant spina bifida. Here, through single-cell transcriptomics we show that at E8.5, the time-point preceding mouse neural tube closure, co-expression of <i>Grhl3</i>, <i>Tfap2a</i>, and <i>Tfap2c</i> defines a previously unrecognised progenitor population of surface ectoderm integral for neural tube closure. Deletion of <i>Grhl3</i> expression in this cell population using a <i>Tfap2a-Cre</i> transgene recapitulates the spina bifida observed in <i>Grhl3</i>-null animals. Moreover, conditional inactivation of <i>Tfap2c</i> expression in <i>Grhl3</i>-expressing neural plate border cells also induces spina bifida. These findings indicate that a specific neural plate border cellular cohort is required for the early-stage neurulation.