BACKGROUND AND PURPOSE: Waardenburg syndrome, characterized by deafness and pigmentation abnormalities, is clinically and genetically heterogeneous, consisting of 4 distinct subtypes and involving several genes. SOX10 mutations have been found both in types 2 and 4 Waardenburg syndrome and neurologic variants. The purpose of this study was to evaluate both the full spectrum and relative frequencies of inner ear malformations in these patients.

Autosomal recessive microcephaly or microcephaly primary hereditary (MCPH) is a genetically heterogeneous neurodevelopmental disorder characterized by a reduction in brain volume, indirectly measured by an occipitofrontal circumference (OFC) 2 standard deviations or more below the age- and sex-matched mean (-2SD) at birth and -3SD after 6 months, and leading to intellectual disability of variable severity. The abnormal spindle-like microcephaly gene (ASPM), the human ortholog of the Drosophila melanogaster "abnormal spindle" gene (asp), encodes ASPM, a protein localized at the centrosome of apical neuroprogenitor cells and involved in spindle pole positioning during neurogenesis. Loss-of-function mutations in ASPM cause MCPH5, which affects the majority of all MCPH patients worldwide. Here, we report 47 unpublished patients from 39 families carrying 28 new ASPM mutations, and conduct an exhaustive review of the molecular, clinical, neuroradiological, and neuropsychological features of the 282 families previously reported (with 161 distinct ASPM mutations). Furthermore, we show that ASPM-related microcephaly is not systematically associated with intellectual deficiency and discuss the association between the structural brain defects (strong reduction in cortical volume and surface area) that modify the cortical map of these patients and their cognitive abilities.

CHARGE syndrome (OMIM #214800) is a multiple malformation syndrome with distinctive diagnostic criteria, usually because of CHD7 (chromodomain helicase DNA binding 7) haploinsufficiency. Familial occurrence of CHARGE syndrome is rare. We report six patients from two Caucasian families (both with one parent and two children) affected by mild to severe CHARGE syndrome. Direct sequencing of the CHD7 gene was performed in these two unrelated families. A mutation in exon 8 (c.2501C>T - p.S834F) in first chromodomain was found in family A and a nonsense mutation in exon 2 (c.469C>T - p.R157X) in family B. Both mutations are de novo in the parents. In family A, the elder son had bilateral cleft lip and palate, esophageal atresia with fistula, complex heart defect and vertebral abnormalities, while the younger had a posterior coloboma. Their mother had asymptomatic vestibular dysfunction and retinal coloboma, identified after the molecular diagnosis of her children. In family B, both affected children had severe expression of CHARGE syndrome. The father carrying the mutation only had asymmetric anomaly of the pinnae. These familial reports describe the intrafamilial variability of CHARGE syndrome, and underline the presence of CHD7 mutations in patients who do not fit the 'classical clinical criteria' for CHARGE syndrome.

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Fibroblast growth factor receptor 3 (FGFR3) is a key regulator of skeletal development and activating mutations in FGFR3 cause skeletal dysplasias, including hypochondroplasia, achondroplasia and thanatophoric dysplasia. The introduction of the Y367C mutation corresponding to the human Y373C thanatophoric dysplasia type I (TDI) mutation into the mouse genome, resulted in dwarfism with a skeletal phenotype remarkably similar to that of human chondrodysplasia. To investigate the role of the activating Fgfr3 Y367C mutation in auditory function, the middle and inner ear of the heterozygous mutant Fgfr3(Y367C/+) mice were examined. The mutant Fgfr3(Y367C/+) mice exhibit fully penetrant deafness with a significantly elevated auditory brainstem response threshold for all frequencies tested. The inner ear defect is mainly associated with an increased number of pillar cells or modified supporting cells in the organ of Corti. Hearing loss in the Fgfr3(Y367C/+) mouse model demonstrates the crucial role of Fgfr3 in the development of the inner ear and provides novel insight on the biological consequences of FGFR3 mutations in chondrodysplasia.