Molecular analysis of spinocerebellar ataxia trinucleotide repeat behavior in normal individuals of a Brazilian population

Ataxin-2 intermediate-length polyglutamine: a possible risk factor for Chinese patients with amyotrophic lateral sclerosis

Intermediate-length polyglutamine (polyQ) expansions in the ataxin-2 (ATXN2) gene have recently been identified as a risk factor for sporadic amyotrophic lateral sclerosis (SALS). Our study aims to analyze cytosine, adenine, guanine (CAG)n expansions in the ATXN2 gene among Chinese patients with SALS. All patients diagnosed with adult-onset sporadic amyotrophic lateral sclerosis (ALS) were consecutively followed up, and their clinical characteristics were collected. To measure the repeat length of ATXN2 polyQ, fluorescence-polymerase chain reaction products were analyzed on a 3100-Avant Genetic Analyzer Applied Biosystem (Foster City, CA, USA) using the ROC-500 size standard. Three hundred forty-five patients with SALS were studied. The mean age of onset was 51.38 ± 12.45 years. ATXN2 polyQ with a repeat length greater than 27 was found to be weakly associated with amyotrophic lateral sclerosis in our study. There was no significant difference in mean age of onset, gender, and onset site between the group of SALS patients with and without ATXN2 polyQ expansion greater than 27. Our finding provides evidence that the ATXN2 polyQ expansion greater than 27 might be a risk factor for Chinese SALS patients.

3.2 Mb microdeletion in chromosome 7 bands q22.2-q22.3 associated with overgrowth and delayed bone age

We report a patient with mental retardation, epilepsy, overgrowth, delayed bone age, peculiar facial features, corpus callosum hypoplasia, enlarged cisterna magna and right cerebellar hypoplasia. Array-CGH analysis revealed the presence of a de novo 3.2 Mb interstitial deletion of the long arm of chromosome 7 involving bands q22.2-q22.3. The rearrangement includes 15 genes and encompasses a genomic region that represents a site of frequent loss of heterozygosity in myeloid malignancies. Four genes are implicated in the control of cell cycle: SRPK2, MLL5, RINT1 and LHFPL3. Haploinsufficiency of these genes might therefore be associated with overgrowth and could confer susceptibility to cancers or other tumours, so that attention to this possibility would be appropriate during regular medical review. In conclusion, array-CGH analysis should be performed in patients with overgrowth where the known causes have already been excluded, because some still unclassified overgrowth syndromes may be caused by subtle genomic imbalances.