ABSTRACT
BACKGROUND: Genetic linkage studies have identified two susceptibility loci for essential tremor (ET) on chromosomes 3q13 (ETM1) and 2p24.1 (ETM2). Linkage disequilibrium studies in separate population samples from the United States and Singapore suggest an association between ET and loci at ETM2. METHODS: Fine mapping studies were conducted on multiplex and singleton US families linked to ETM2 using newly detected loci within the candidate interval to establish the minimal critical region (MCR) harboring an ET gene. The genes and transcripts within this interval were systematically analyzed by single-strand conformational polymorphism analysis and DNA sequencing. RESULTS: A 464-kb region between loci D2S2150 and etm1231 was defined as the MCR. The coding regions and flanking intronic splice sites of two genes and seven transcripts in this interval were evaluated for mutations. A missense mutation (828C-->G) in the transcript FLJ14249 (HS1-BP3) was identified in one US family. This mutation was found in another apparently unrelated US family with ET and was absent in 150 control samples (300 chromosomes). The 828C-->G mutation causes a substitution of a glycine for an alanine residue in the HS1-BP3 protein. The HS1-BP3 protein binds to proteins that are highly expressed in motor neurons and Purkinje cells and regulate the Ca2+/calmodulin-dependent protein kinase activation of tyrosine and tryptophan hydroxylase. CONCLUSIONS: A rare variant in the HS1-BP3 gene that is associated with essential tremor (ET) in two families is reported. This finding will facilitate research on the functional role of this gene and related genes in the pathogenesis of ET.
Subject(s)
Essential Tremor/genetics , Mutation, Missense , Nerve Tissue Proteins/genetics , Point Mutation , Adult , Age of Onset , Alleles , Amino Acid Substitution , Chromosomes, Human, Pair 2/genetics , DNA Mutational Analysis , Essential Tremor/epidemiology , Female , Genes, Dominant , Haplotypes/genetics , Humans , Lod Score , Male , Nerve Tissue Proteins/physiology , Pedigree , Polymorphism, Single-Stranded Conformational , Reverse Transcriptase Polymerase Chain Reaction , Singapore/epidemiology , United States/epidemiologyABSTRACT
An ancestral haplotype on chromosome 2p24.1 described in an American sample with familial essential tremor (ET) was analyzed in a different ethnic sample from Singapore. Six polymorphic loci (etm1240, etm1231, etm1234, APOB, etm1241, and etm1242) in a 274-kb interval within an ET gene candidate region (ETM2) were analyzed in Singaporean individuals with a family history of ET (n = 52) and compared to Singaporean controls older than age 65 (n = 49). The allele frequencies were significantly different between cases and controls for the loci etm1234 (p = 0.0001) and APOB (p = 0.0320). An extended haplotype formed by the loci etm1231, etm1234, and APOB occurred with a frequency of 31% in Singaporean cases and in 1.8% of elderly Singaporean controls (p = 0.0005). Haplotype studies in two different population samples suggest that a disease locus for ET lies near or within the 100-kb interval between the loci etm1231 and APOB.
Subject(s)
Apolipoproteins B/genetics , Essential Tremor/genetics , Haplotypes/genetics , Adolescent , Adult , Aged , Aged, 80 and over , Case-Control Studies , Chromosomes, Human, Pair 2 , Essential Tremor/diagnosis , Essential Tremor/epidemiology , Female , Gene Frequency , Genetic Variation , Genotype , Humans , Male , Microsatellite Repeats , Middle Aged , Singapore/epidemiologyABSTRACT
A mild type of autosomal recessive, non-syndromic mental retardation (NSMR) is linked to loci on chromosome 3p. This report delimits the MRT2A minimal critical region to 4.2 Mb between loci D3S3630 and D3S1304. This interval contains nine genes (IL5RA, TRNT1, LRRN1, SETMAR, SUMF1, ITPR1, BHLHB2, EDEM, and MRPS36P1). The results suggest that a mutation does not exist in these genes and that an unknown transcript in the region contributes to the cognitive deficits in NSMR.
