Homozygosity for a Novel DOCK7 Variant Due to Segmental Uniparental Isodisomy of Chromosome 1 Associated with Early Infantile Epileptic Encephalopathy (EIEE) and Cortical Visual Impairment

被引:3
|
作者
Pfiffner, Fatma Kivrak [1 ]
Koller, Samuel [1 ]
Menetrey, Anika [2 ]
Graf, Urs [1 ]
Baehr, Luzy [1 ]
Maspoli, Alessandro [1 ]
Hackenberg, Annette [2 ]
Kottke, Raimund [3 ]
Gerth-Kahlert, Christina [4 ]
Berger, Wolfgang [1 ,5 ,6 ,7 ]
机构
[1] Univ Zurich, Inst Med Mol Genet, Wagistr 1, CH-8952 Schlieren, Switzerland
[2] Univ Zurich, Univ Childrens Hosp, Dept Pediat Neurol, CH-8032 Zurich, Switzerland
[3] Univ Zurich, Univ Childrens Hosp, Dept Diagnost Imaging, CH-8032 Zurich, Switzerland
[4] Univ Hosp, Dept Ophthalmol, CH-8091 Zurich, Switzerland
[5] Zurich Univ, Neurosci Ctr, CH-8057 Zurich, Switzerland
[6] Swiss Fed Inst Technol, CH-8057 Zurich, Switzerland
[7] Univ Zurich, Ctr Integrat Human Physiol, CH-8057 Zurich, Switzerland
关键词
uniparental disomy (UPD); mUPiD; UPiD; UPhD; loss of heterozygosity (LOH); early infantile epileptic encephalopathy 23; EIEE23; cortical blindness; cortical visual impairment; DISOMY UPD; PATIENT; MUTATION; GENE; MOSAICISM; MECHANISM;
D O I
10.3390/ijms23137382
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Early infantile epileptic encephalopathy (EIEE) is a severe neurologic and neurodevelopmental disease that manifests in the first year of life. It shows a high degree of genetic heterogeneity, but the genetic origin is only identified in half of the cases. We report the case of a female child initially diagnosed with Leber congenital amaurosis (LCA), an early-onset retinal dystrophy due to photoreceptor cell degeneration in the retina. The first examination at 9 months of age revealed no reaction to light or objects and showed wandering eye movements. Ophthalmological examination did not show any ocular abnormalities. The patient displayed mildly dysmorphic features and a global developmental delay. Brain MRI demonstrated pontine hypo-/dysplasia. The patient developed myoclonic epileptic seizures and epileptic spasms with focal and generalized epileptiform discharges on electroencephalogram (EEG) at the age of 16 months. Genetic screening for a potentially pathogenic DNA sequence variant by whole-exome sequencing (WES) revealed a novel, conserved, homozygous frameshift variant (c.5391delA, p.(Ala1798LeufsTer59)) in exon 42 of the DOCK7 gene (NM_001271999.1). Further analysis by SNP array (Karyomapping) showed loss of heterozygosity (LOH) in four segments of chromosome 1. WES data of the parents and the index patient (trio analysis) demonstrated that chromosome 1 was exclusively inherited from the mother. Four LOH segments of chromosome 1 alternately showed isodisomy (UPiD) and heterodisomy (UPhD). In WES data, the father was a noncarrier, and the mother was heterozygous for this DOCK7 variant. The DOCK7 gene is located in 1p31.3, a region situated in one of the four isodisomic segments of chromosome 1, explaining the homozygosity seen in the affected child. Finally, Sanger sequencing confirmed maternal UPiD for the DOCK7 variant. Homozygous or compound heterozygous pathogenic variants in the DOCK7 (dedicator of cytokinesis 7) gene are associated with autosomal recessive, early infantile epileptic encephalopathy 23 (EIEE23; OMIM #615,859), a rare and heterogeneous group of neurodevelopmental disorders diagnosed during early childhood. To our knowledge, this is the first report of segmental uniparental iso- and heterodisomy of chromosome 1, leading to homozygosity of the DOCK7 frameshift variant in the affected patient.
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页数:11
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