Spinocerebellar ataxias (SCAs) are a heterogeneous group of autosomal-dominant neurodegenerative disorders involving the cerebellum and 23 different genes. We mapped SCA38 to a 56 Mb region on chromosome 6p in a SCA-affected Italian family by whole-genome linkage analysis. Targeted resequencing identified a single missense mutation (c.689G>T [p.Gly230Val]) in ELOVL5. Mutation screening of 456 independent SCA-affected individuals identified the same mutation in two further unrelated Italian families. Haplotyping showed that at least two of the three families shared a common ancestor. One further missense variant (c.214C>G [p.Leu72Val]) was found in a French family. Both missense changes affect conserved amino acids, are predicted to be damaging by multiple bioinformatics tools, and were not identified in ethnically matched controls or within variant databases. ELOVL5 encodes an elongase involved in the synthesis of polyunsaturated fatty acids of the ω3 and ω6 series. Arachidonic acid and docosahexaenoic acid, two final products of the enzyme, were reduced in the serum of affected individuals. Immunohistochemistry on control mice and human brain demonstrated high levels in Purkinje cells. In transfection experiments, subcellular localization of altered ELOVL5 showed a perinuclear distribution with a signal increase in the Golgi compartment, whereas the wild-type showed a widespread signal in the endoplasmic reticulum. SCA38 and SCA34 are examples of SCAs due to mutations in elongase-encoding genes, emphasizing the importance of fatty-acid metabolism in neurological diseases.

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The gene encoding the brain-derived neurotrophic factor (BDNF) has been demonstrated as a candidate for Alzheimer's disease-related depression (AD-D) susceptibility. Additionally, an association between AD-D and the functional valine to methionine (Val66Met) polymorphism has been reported. The aim of this study was to assess the genetic contribution of other BDNF variants to AD-D. Two-hundred forty-five AD patients were divided into two subgroups according to the presence (AD-D) or the absence (AD-nD) of depressive symptoms. Four single-nucleotide polymorphisms within BDNF gene were considered, i.e., C270T, rs2049045 C/G, G196A (Val66Met), and G11757C. In our sample, 35.5% of patients (n = 87) reported AD-related depressive symptoms. The individual SNP analysis showed an association between G196A and G11757C genotypes and AD-D. Accordingly, considering the allele frequencies, BDNF 196*A allele was significantly overrepresented in AD-D compared to AD-nD (OR = 1.80, 95% CI = 1.19-2.72), as well as BDNF 11757*C allele (OR = 1.90, 95% CI = 1.25-2.90). Haplotype analyses revealed that the alleles at four loci (C270T, rs2049045 C/G, G196A, G11757C) interacted to further increase the risk of AD-D. Compared to the most common not-at-risk C-C-G-G haplotype, C-G-A-C (OR = 3.55, 95% CI = 1.44-8.76, P = 0.006) and C-C-A-C haplotypes (OR = 1.72, 95% CI = 1.03-2.87, P = 0.037) were overrepresented in AD-D. This study suggests that BDNF genetic variations play a role in the susceptibility to AD-related depression.

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