Autosomal recessive frontotemporal pachygyria

Mutations in CRADD Result in Reduced Caspase-2-Mediated Neuronal Apoptosis and Cause Megalencephaly with a Rare Lissencephaly Variant

Lissencephaly is a malformation of cortical development typically caused by deficient neuronal migration resulting in cortical thickening and reduced gyration. Here we describe a “thin” lissencephaly (TLIS) variant characterized by megalencephaly, frontal predominant pachygyria, intellectual disability, and seizures. Trio-based whole-exome sequencing and targeted re-sequencing identified recessive mutations of CRADD in six individuals with TLIS from four unrelated families of diverse ethnic backgrounds. CRADD (also known as RAIDD) is a death-domain-containing adaptor protein that oligomerizes with PIDD and caspase-2 to initiate apoptosis. TLIS variants cluster in the CRADD death domain, a platform for interaction with other death-domain-containing proteins including PIDD. Although caspase-2 is expressed in the developing mammalian brain, little is known about its role in cortical development. CRADD/caspase-2 signaling is implicated in neurotrophic factor withdrawal- and amyloid-β-induced dendritic spine collapse and neuronal apoptosis, suggesting a role in cortical sculpting and plasticity. TLIS-associated CRADD variants do not disrupt interactions with caspase-2 or PIDD in co-immunoprecipitation assays, but still abolish CRADD’s ability to activate caspase-2, resulting in reduced neuronal apoptosis in vitro. Homozygous Cradd knockout mice display megalencephaly and seizures without obvious defects in cortical lamination, supporting a role for CRADD/caspase-2 signaling in mammalian brain development. Megalencephaly and lissencephaly associated with defective programmed cell death from loss of CRADD function in humans implicate reduced apoptosis as an important pathophysiological mechanism of cortical malformation. Our data suggest that CRADD/caspase-2 signaling is critical for normal gyration of the developing human neocortex and for normal cognitive ability.

"Reverse Tigroid" Pattern in Pachygyria: A Novel Finding

Pachygyria is considered a subtype of lissencephaly which, in turn, is a spectrum of disorders caused by abnormal neuronal migration. Clinical presentation in this disorder may be varied including microcephaly, developmental delay, facial dysmorphism, seizures, and mental retardation. Magnetic resonance imaging (MRI) of brain identifies the exact nature and extent of the disease and helps in delineating further plan of management. A Tigroid pattern on axial MRI scan and leopard pattern on a sagittal plane has been classically reported in disorders of myelin formation such as metachromatic leukodystrophy and Pelizaeus–Merzbacher disease. We present here a case of pachygyria who presented to us with some atypical features including “tigroid-like stripes” and “leopard-like pattern” on MRI brain which has not been reported in the medical literature previously.

Frontotemporal pachygyria-two new patients

We describe two Finnish brothers with frontotemporal pachygyria, intellectual deficiency and mild dysmorphisms. Previously, only a few cases of similar frontotemporal pachygyria have been reported. This report provides further evidence about frontotemporal pachygyria being a distinct genetic entity inherited as an autosomal recessive trait.

Apparently novel genetic syndrome of pachygyria, mental retardation, seizure, and arachnoid cysts

We report on an apparently new syndrome in a consanguineous family with seven members, three of whom have cerebral anomalies including pachygyria and arachnoid cysts along with mental retardation and seizures. The two patients with seizure disorders also had multiple enlarged perivascular spaces seen in the white matter of the centrum semiovale. Our data provide a contribution to the accumulating knowledge on familial cerebral anomalies including arachnoid cysts and lissencephaly. Given the lack of mutation in known lissencephaly genes such as LIS1, 14-3-3epsilon, and DCX, this syndrome may constitute a new phenotype with autosomal recessive inheritance.

Frontotemporal abnormal gyration with infantile spasms in identical twins

We describe the case of 10-year-old twin girls, who were born to nonconsanguineous parents and showed pes equinovarus, infantile spasms, and severe psychomotor retardation. Neither patient showed marked microcephaly. Neuroimaging revealed a simplified gyral pattern in the bilateral frontotemporal areas, a reduced volume of cerebral white matter, and a thin corpus callosum in both patients. The cerebral cortex presented with significant thickness in the anterior temporal region at the age of 10 years, which suggest that the simplified gyri can evolve into the pachygyria during postnatal period. These cases may represent a hereditary brain malformation with a distinct pattern of abnormal cortical gyration. The age-dependent change in appearance of dysgenetic cortex should be further explored in cases with brain malformations.

Genetics of the polymicrogyria syndromes

Polymicrogyria is a relatively common malformation of cortical development, characterised by multiple small gyri with abnormal cortical lamination. The different forms of polymicrogyria encompass a wide range of clinical, aetiological, and histological findings. Advances in imaging have improved the diagnosis and classification of the condition. The molecular basis of polymicrogyria is beginning to be elucidated with the identification of a gene, GPR56, for bilateral frontoparietal polymicrogyria. Functional studies of the GPR56 gene product will yield insights not only into the causes of polymicrogyria but also into the mechanisms of normal cortical development and the regional patterning of the cerebral cortex. Based on imaging studies, several other region specific patterns of polymicrogyria have been identified, and there is increasing evidence that these may also have a significant genetic component to their aetiology. This paper reviews current knowledge of the different polymicrogyria syndromes, with discussion of clinical and imaging features, patterns of inheritance, currently mapped loci, candidate genes, chromosomal abnormalities, and implications for genetic counselling.