Microtubules, polarity and vertebrate neural tube morphogenesis

Microtubules (MTs) are key cellular components, long known to participate in morphogenetic events that shape the developing embryo. However, the links between the cellular functions of MTs, their effects on cell shape and polarity, and their role in large-scale morphogenesis remain poorly understood. Here, these relationships were examined with respect to two strategies for generating the vertebrate neural tube: bending and closure of the mammalian neural plate; and cavitation of the teleost neural rod. The latter process has been compared with 'secondary' neurulation that generates the caudal spinal cord in mammals. MTs align along the apico-basal axis of the mammalian neuroepithelium early in neural tube closure, participating functionally in interkinetic nuclear migration, which indirectly impacts on cell shape. Whether MTs play other functional roles in mammalian neurulation remains unclear. In the zebrafish, MTs are important for defining the neural rod midline prior to its cavitation, both by localizing apical proteins at the tissue midline and by orienting cell division through a mirror-symmetric MT apparatus that helps to further define the medial localization of apical polarity proteins. Par proteins have been implicated in centrosome positioning in neuroepithelia as well as in the control of polarized morphogenetic movements in the neural rod. Understanding of MT functions during early nervous system development has so far been limited, partly by techniques that fail to distinguish 'cause' from 'effect'. Future developments will likely rely on novel ways to selectively impair MT function in order to investigate the roles they play

Currarino syndrome: repair of the dysraphic anomalies and resection of the presacral mass in a combined neurosurgical and general surgical approach

OBJECTIVE: It is well established that Currarino syndrome (CS) may be associated with spinal dysraphism. Here, the authors report on 10 CS patients with dysraphic anomalies who had undergone a combined neurosurgical and general surgical approach to repair the dysraphic anomalies and resect the presacral mass in a single operation. They discuss the spectrum of spinal dysraphism that may coexist in CS in the context of its developmental etiology. METHODS: Children with a confirmed CS diagnosis who had undergone the combined operative approach were identified from a departmental database. Presenting features were recorded and preoperative imaging was analyzed to record features of the presacral mass and the dysraphic anomalies. The histopathological nature of the resected presacral mass and the outcomes postoperatively and at the last follow-up were reviewed. RESULTS: Between 2008 and 2015, 10 patients presented with CS, 9 with constipation. Median age at the time of surgery was 1.3 years. Six of the 10 patients had anorectal malformation consisting of anal stenosis, rectal stenosis, or imperforate anus. Spinal anomalies included anterior meningocele (5 cases), low-lying conus (8), terminal syrinx (4), fatty filum (5), caudal lipoma (3), and intraspinal cyst (1). In all cases, the lumbosacral spinal canal was accessed via a midline approach with laminoplasty, allowing spinal cord untethering and repair of the dysraphic anomalies. Following dural closure, the incision was extended inferiorly to incorporate a posterior sagittal approach to resect the presacral mass. The histopathological nature of the mass was mature teratoma (8 cases), complex hamartomatous malformation (1), or neurenteric cyst (1). There were no new instances of neurological deterioration, with most instances of persisting morbidity related to constipation (6 cases) or neurogenic bladder dysfunction (8). There were no infective complications, no instances of cerebrospinal fluid fistula, no recurrences of the presacral mass, and no cases of retethering of the spinal cord. CONCLUSIONS: Although not part of the original triad, spinal dysraphic anomalies are common in CS and in keeping with a disorder of secondary neurulation. Lumbosacral MRI is an essential investigation when CS is suspected. Children are at risk of sphincter impairment due to the anorectal malformation; however, both spinal cord tethering and compression from the presacral mass may further compromise long-term continence. A combined operative approach to repair the dysraphic anomalies and resect the presacral mass is described with good postoperative and long-term outcomes