Callosal agenesis and congenital mirror movements: outcomes associated with DCC mutations. Developmental Medicine and Child Neurology (2020). doi:10.1111/dmcn.14486.

Pathogenic variants in the gene encoding deleted in colorectal cancer (DCC) are the first genetic cause of isolated agenesis of the corpus callosum (ACC). Here we present the detailed neurological, brain magnetic resonance imaging (MRI), and neuropsychological characteristics of 12 individuals from three families with pathogenic variants in DCC (aged 8–50y), who showed ACC and mirror movements (n=5), mirror movements only (n=2), ACC only (n=3), or neither ACC nor mirror movements (n=2). There was heterogeneity in the neurological and neuroimaging features on brain MRI, and performance across neuropsychological domains ranged from extremely low (impaired) to within normal limits (average). Our findings show that ACC and/or mirror movements are associated with low functioning in select neuropsychological domains and a DCC pathogenic variant alone is not sufficient to explain the disability.

The deleted in colorectal cancer (DCC) gene encodes the netrin-1 (NTN1) receptor DCC, a transmembrane protein required for the guidance of commissural axons. Germline DCC mutations disrupt the development of predominantly commissural tracts in the central nervous system (CNS) and cause a spectrum of neurological disorders. Monoallelic, missense, and predicted loss-of-function DCC mutations cause congenital mirror movements, isolated agenesis of the corpus callosum (ACC), or both. Biallelic, predicted loss-of-function DCC mutations cause developmental split brain syndrome (DSBS). Although the underlying molecular mechanisms leading to disease remain poorly understood, they are thought to stem from reduced or perturbed NTN1 signaling. Here, we review the 26 reported DCC mutations associated with abnormal CNS development in humans, including 14 missense and 12 predicted loss-of-function mutations, and discuss their associated clinical characteristics and diagnostic features. We provide an update on the observed genotype-phenotype relationships of congenital mirror movements, isolated ACC and DSBS, and correlate this to our current understanding of the biological function of DCC in the development of the CNS. All mutations and their associated phenotypes were deposited into a locus-specific LOVD (https://databases.lovd.nl/shared/genes/DCC).

Mutations in DCC cause isolated agenesis of the corpus callosum with incomplete penetrance.  Nature Genetics  49, 511–514

Brain malformations involving the corpus callosum are common in children with developmental disabilities. We identified DCC mutations in four families and five sporadic individuals with isolated agenesis of the corpus callosum (ACC) without intellectual disability. DCC mutations result in variable dominant phenotypes with decreased penetrance, including mirror movements and ACC associated with a favorable developmental prognosis. Possible phenotypic modifiers include the type and location of mutation and the sex of the individual.

Authors:

Ashley P L Marsh, Delphine Heron, Timothy J Edwards, Angélique Quartier, Charles Galea, Caroline Nava, Agnès Rastetter, Marie-Laure Moutard, Vicki Anderson, Pierre Bitoun, Jens Bunt, Anne Faudet, Catherine Garel, Greta Gillies, Ilan Gobius, Justine Guegan, Solveig Heide, Boris Keren, Fabien Lesne, Vesna Lukic, Simone A Mandelstam, George McGillivray, Alissandra McIlroy, Aurélie Méneret, Cyril Mignot, Laura R Morcom, Sylvie Odent, Annalisa Paolino, Kate Pope, Florence Riant, Gail A Robinson, Megan Spencer-Smith, Myriam Srour, Sarah E M Stephenson, Rick Tankard, Oriane Trouillard, Quentin Welniarz, Amanda Wood, Alexis Brice, Guy Rouleau, Tania Attié-Bitach, Martin B Delatycki, Jean-Louis Mandel, David J Amor, Emmanuel Roze, Amélie Piton, Melanie Bahlo, Thierry Billette de Villemeur, Elliott H Sherr, Richard J Leventer, Linda J Richards, Paul J Lockhart & Christel Depienne