RESUMO
BACKGROUND: The overall birth prevalence for congenital malformations of the central nervous system (CNS) among Europeans may be as high as 1 in 100 live births. The etiological factors remain largely unknown. The aim of this study was to detect causative copy number variations (CNVs) in fetuses of terminated pregnancies with prenatally detected isolated brain malformations. METHODS: Array-based molecular karyotyping was performed in a cohort of 35 terminated fetuses with isolated CNS malformations. Identified putative disease-causing CNVs were confirmed using quantitative polymerase chain reaction or multiplex ligation-dependent probe amplification. RESULTS: Based on their de novo occurrence and/or their established association with congenital brain malformations, we detected five disease-causing CNVs in four fetuses involving chromosomal regions 6p25.1-6p25.3 (FOXC1), 6q27, 16p12.3, Xp22.2-Xp22.32 (MID1), and Xp22.32-Xp22.33. Furthermore, we detected a probably disease-causing CNV involving chromosomal region 3p26.3 in one fetus, and in addition, we detected 12 CNVs in nine fetuses of unknown clinical significance. All CNVs except for two were absent in 1307 healthy in-house controls (frequency <0.0008). Each of the two CNVs present in in-house controls was present only once (frequency = 0.0008). Furthermore, our data suggests the involvement of CNTN6 and KLHL15 in the etiology of agenesis of the corpus callosum, the involvement of RASD1 and PTPRD in Dandy-Walker malformation, and the involvement of ERMARD in ventriculomegaly. CONCLUSIONS: Our study suggests that CNVs play an important role in the etiology of isolated brain malformations.
RESUMO
BACKGROUND: For the majority of congenital brain malformations, the underlying cause remains unknown. Recent studies have implicated rare copy number variations (CNVs) in their etiology. METHODS: Here, we used array-based molecular karyotyping to search for causative CNVs in 33 fetuses of terminated pregnancies with prenatally detected brain malformations and additional extracerebral anomalies. RESULTS: In 11 fetuses, we identified 15 CNVs (0.08 Mb to 29.59 Mb), comprising four duplications and eleven deletions. All larger CNVs (> 5 Mb) had also been detected by prenatal conventional karyotyping. None of these CNVs was present in our 1307 healthy in-house controls (frequency < 0.0008). Among these CNVs, we prioritized six chromosomal regions (1q25.1, 5q35.1, 6q25.3-qter, 11p14.3, 15q11.2-q13.1, 18q21.1) due to their previous association with human brain malformations or owing to the presence of a single gene expressed in human brain. Prioritized genes within these regions were UBTD2, SKA1, SVIP, and, most convincingly, GPR52. However, re-sequencing of GPR52 in 100 samples from fetuses with brain malformations or patients with intellectual disability and brain malformations revealed no disease-causing mutation. CONCLUSION: Our study suggests chromosomal regions 1q25.1, 5q35.1, 6q25.3-qter, 11p14.3, 15q11.2-q13.1, and 18q21.1 to be involved in human brain development. Within three of these regions, we suggest UBTD2, GPR52, and SKA1 as possible candidate genes. Because the overall detection rate of array-based molecular karyotyping was slightly higher (23%) than that of conventional prenatal karyotyping (20%), we suggest it's use for prenatal diagnostic testing in fetuses with nonisolated brain malformations.
