A Family with Mental Retardation, Epilepsy and Cerebellar Hypoplasia Showing Linkage to Chromosome 20p11.21-q11.23.

BACKGROUND: Cerebellar hypoplasia (CH) is a rare malformation caused by various etiologies, usually manifesting clinically as nonprogressive cerebellar ataxia with or without mental retardation. The molecular pathogenesis of the autosomal recessive cerebellar ataxias has a wide range of mechanisms. Differential diagnosis and categorization of the recessive cerebellar ataxias, however, need more specific, biochemical and genetic investigation. METHODS: This study applied whole-genome linkage analysis to study a family with nonprogressive cerebellar ataxia and additional mental retardation, epilepsy, and facial dysmorphic features. Genotyping and linkage analysis was done using the GeneChip Mapping 250K NspI Array (Affymetrix Inc., Santa Clara, Calif., USA) for genome-wide linkage analysis of the genotyping data from the affected children and their parents. RESULTS: Allegro software version 1.2 was used for multipoint linkage analysis. We assumed an autosomal recessive inheritance pattern and assigned a penetrance of 0.999. Single-nucleotide polymorphism allele frequencies were estimated from the Affymetrix data of the Caucasian family studied. Using these parameters, a theoretical maximum logarithm of the odds score of 2.69 was identified at chromosome 20p11.21-q11.23. CONCLUSIONS: This chromosomal locus is unprecedented in autosomal recessive and nonprogressive ataxia disorder. Further investigation might reveal a new causative gene generating the CH phenotype.

Mutation in MEOX1 gene causes a recessive Klippel-Feil syndrome subtype.

BACKGROUND: Klippel-Feil syndrome (KFS) is characterized by the developmental failure of the cervical spine and has two dominantly inherited subtypes. Affected individuals who are the children of a consanguineous marriage are extremely rare in the medical literature, but the gene responsible for this recessive trait subtype of KFS has recently been reported. RESULTS: We identified a family with the KFS phenotype in which their parents have a consanguineous marriage. Radiological examinations revealed that they carry fusion defects and numerical abnormalities in the cervical spine, scoliosis, malformations of the cranial base, and Sprengel's deformity. We applied whole genome linkage and whole-exome sequencing analysis to identify the chromosomal locus and gene mutated in this family. Whole genome linkage analysis revealed a significant linkage to chromosome 17q12-q33 with a LOD score of 4.2. Exome sequencing identified the G > A p.Q84X mutation in the MEOX1 gene, which is segregated based on pedigree status. Homozygous MEOX1 mutations have reportedly caused a similar phenotype in knockout mice. CONCLUSIONS: Here, we report a truncating mutation in the MEOX1 gene in a KFS family with an autosomal recessive trait. Together with another recently reported study and the knockout mouse model, our results suggest that mutations in MEOX1 cause a recessive KFS phenotype in humans.

A novel locus for restless legs syndrome on chromosome 13q.

BACKGROUND: Restless legs syndrome (RLS) is a sensorimotor disorder in which affected individuals suffer from uncomfortable sensations and an urge to move their lower limbs; it occurs mainly in resting situations during the evening or at night. Multiple chromosomal loci have been mapped for RLS through family-based linkage analysis, and genome-wide association studies but causative mutations have not been identified yet. METHOD: We identified an RLS family from the eastern part of central Turkey which has 10 patients suffering from this syndrome. Whole genome linkage analysis was performed in family members who consented for study (9 affected and 2 unaffected). RESULTS: A theoretical maximum logarithm of the odds score of 3.29 was identified at chromosome 13q32.3-33.2. This result shows strong genetic linkage to this locus. CONCLUSIONS: We demonstrated a genetic linkage at chromosome 13 in a RLS family. Further investigation in this linkage area may reveal a causative gene leading to RLS phenotype and may illuminate the pathogenesis of this disease. This study supports the genetic heterogeneity in the pathogenesis of this syndrome.

Intracranial arachnoid cyst family with autosomal recessive trait mapped to chromosome 6q22.31-23.2.

BACKGROUND: Arachnoid cysts are congenital fluid-filled compartments within the cerebrospinal fluid cisterns and cerebral fissures. They most commonly occur sporadically, and familial occurrence has rarely been reported. In this study, we showed the first genetic linkage in the literature in a pure intracranial arachnoid cyst family with autosomal recessive trait. METHODS: We identified an intracranial arachnoid cyst family in southern Turkey whose six of seven offspring had intracranial arachnoid cysts in different localizations, and collected venous blood from seven offspring of the family. Whole-genome linkage analysis was performed in all offspring. RESULTS: A theorical maximum logarithm of the odds score of 4.6 was identified at chromosome 6q22.31-23.2. This result shows strong genetic linkage to this locus. CONCLUSIONS: We present the first genetic linkage analysis result in a pure intracranial arachnoid cyst family in literature. Further investigation of this linkage area can reveal a causative gene causing the intracranial arachnoid cyst phenotype and can illuminate the pathogenesis of this disease.