Periventricular neuronal heterotopia, oro-facio-digital anomalies, and microphthalmia. A new syndrome?:

Periventricular nodular heterotopia and distal limb deficiency: a recurrent association

Malformations of cerebral cortical development, in particular periventricular nodular heterotopia (PNH), and distal transverse limb deficiency have been reported as associated congenital anomalies. Patients with PNH and transverse limb deficiency can be classified as having amniotic band sequence or Adams-Oliver syndrome (AOS). Controversy exists whether these should be considered separate entities. In some AOS patients, autosomal recessive inheritance has been shown, but in most patients causes are unknown, and both environmental and genetic factors have been implicated. We present three patients with PNH and distal transverse limb deficiency to support the hypothesis that these should be considered part of one group of disorders, and highlight the variable severity of the clinical and neuroradiological phenotype. Chromosome abnormalities were excluded by copy number analysis on 250K SNP microarray data.Research done on limb deficiency as on PNH caused by mutations in known genes, suggests the involvement of vascular developmental pathways. The combination of limb deficiency and PNH may have a common causative mechanism. Recognition and grouping of patients with this combination of abnormalities will help elucidating the cause.

Trouble making the first move: interpreting arrested neuronal migration in the cerebral cortex

Postmitotic cortical neurons that fail to initiate migration can remain near their site of origin and form persistent periventricular nodular heterotopia (PH). In human telencephalon, this malformation is most commonly associated with Filamin-A (FLNa) mutations. The lack of genetic animal models that reliably produce PH has delayed our understanding of the underlying molecular mechanisms. This review examines PH pathogenesis using a new mouse model. Although PH have not been observed in Flna-deficient mice generated thus far, the loss of MEKK4, a regulator of Flna, produces striking PH in mice and offers insight into the mechanisms involved in neuronal migration initiation. Elucidating the basic functions of FLNa and associated molecules is crucial for understanding the causes of PH and for developing prevention for at-risk patients.