Inflammatory genes are upregulated in expanded ataxin-3-expressing cell lines and spinocerebellar ataxia type 3 brains

Spinocerebellar ataxia type 3 (SCA3) is a polyglutamine disorder caused by a CAG repeat expansion in the coding region of a gene encoding ataxin-3. To study putative alterations of gene expression induced by expanded ataxin-3, we performed PCR-based cDNA subtractive hybridization in a cell culture model of SCA3. In rat mesencephalic CSM14.1 cells stably expressing expanded ataxin-3, we found a significant upregulation of mRNAs encoding the endopeptidase matrix metalloproteinase 2 (MMP-2), the transmembrane protein amyloid precursor protein, the interleukin-1 receptor-related Fos-inducible transcript, and the cytokine stromal cell-derived factor 1alpha (SDF1alpha). Immunohistochemical studies of the corresponding or associated proteins in human SCA3 brain tissue confirmed these findings, showing increased expression of MMP-2 and amyloid beta-protein (Abeta) in pontine neurons containing nuclear inclusions. In addition, extracellular Abeta-immunoreactive deposits were detected in human SCA3 pons. Furthermore, pontine neurons of SCA3 brains strongly expressed the antiinflammatory interleukin-1 receptor antagonist, the proinflammatory cytokine interleukin-1beta, and the proinflammatory chemokine SDF1. Finally, increased numbers of reactive astrocytes and activated microglial cells were found in SCA3 pons. These results suggest that inflammatory processes are involved in the pathogenesis of SCA3.

Abnormal pulmonary artery pressure response in asymptomatic carriers of primary pulmonary hypertension gene

BACKGROUND

Familial primary pulmonary hypertension (PPH) is an autosomal-dominant inherited disease with incomplete penetrance and poor prognosis. This study was performed to examine whether asymptomatic carriers of a mutated PPH gene can be identified at an early stage by their pulmonary artery systolic pressure (PASP) response to exercise.

METHODS AND RESULTS

Stress Doppler echocardiography during supine bicycle exercise and genetic linkage analysis were performed on 52 members of 2 families with PPH. In 4 PPH patients, the mean PASP was increased at rest (73+/-16 mm Hg). Fourteen additional family members with normal PASP at rest revealed an abnormal PASP response to exercise (from 23+/-4 to 56+/-11 mm Hg) without secondary cause (abnormal response [AR] group). Twenty-seven other members (NR group) revealed a normal PASP response (maximal pressure <40 mm Hg) to exercise (from 24+/-4 to 37+/-3 mm Hg, P<0. 0001). All 14 AR but only 2 NR members shared the risk haplotype with the PPH patients. The molecular genetic analysis supported linkage to chromosome 2q31-32 with a logarithm of the odds score of 4.4 when the 4 patients and the 14 AR members were classified as affected.

CONCLUSIONS

We conclude that the pathological rise of PASP in asymptomatic family members is linked to chromosome 2q31-32 and is probably an early sign of PPH. Therefore, stress Doppler echocardiography may be a useful tool to identify persons at risk for PPH even before pulmonary artery pressures at rest are elevated.

Investigation of the human serotonin 6 [5-HT6] receptor gene in bipolar affective disorder and schizophrenia

Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter that mediates a wide range of central nervous functions by activating multiple 5-HT receptor subtypes. A possible irregularity of serotonergic neurotransmission has been implicated in a variety of neuropsychiatric diseases. In the present study, we performed a systematic mutation scan of the complete coding region and splice junctions of the 5-HT(6) receptor gene to explore the contribution of this gene to the development of bipolar affective disorder and schizophrenia. Investigating 137 unrelated individuals (including 45 bipolar affective patients, 46 schizophrenic patients, and 46 unrelated controls), we identified six single base substitutions (126G/T, 267C/T, 873+30C/T, 873+128A/C, 1128G/C, 1376T/G). Comparing frequencies between patients and controls, we observed a significant overrepresentation of the 267C allele among bipolar patients (P=0. 023 not corrected for multiple testing). This finding was followed up in an independent sample of 105 bipolar family trios using a family-based association design. Fifty-one transmissions could be examined. In 30 cases allele 267C and in 21 cases allele 267T were transmitted to the affected offspring. Although this result was far from statistical significance (transmission disequilibrium test=1.59, P=0.208), the limited number of possible transmissions may have prevented detection of smaller effects. Our preliminary data suggest that bipolar affective disorder may be associated with variation in the 5-HT(6) gene. It will be important to extend the present analysis to larger samples. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:217-221, 2000.

Genetic linkage analysis with dyslexia: evidence for linkage of spelling disability to chromosome 15

Dyslexia (reading and spelling disability) is one of the most frequently diagnosed disorders in childhood. Twin studies of dyslexia have indicated that deficits in spelling are substantially heritable and that the heritability of spelling deficits is higher than the heritability of reading deficits. We conducted a linkage study for spelling disability in seven multiplex families from Germany. Following previously reported linkage findings of components of dyslexia to chromosome 6p21-p22 and 15q21, we genotyped 26 microsatellite markers covering all of chromosome 6, and 13 microsatellite markers covering all of chromosome 15. While the chromosome 6 data were negative, results from chromosome 15 markers supported a locus on 15q21. The highest two-point LOD score was 1.26 with marker D15S143 at theta = 0. A multipoint LOD score of 1.78 (p = 0.0042) was achieved with a maximum at D15S132. Thus, our results provide independent support for a dyslexia gene on the long arm of chromosome 15.

Cloning, genomic organization, alternative transcripts and mutational analysis of the gene responsible for autosomal recessive universal congenital alopecia

Complete or partial congenital absence of hair (congenital alopecia) may occur isolated or with associated defects. The majority of families with isolated congenital alopecia has been reported to follow an autosomal recessive mode of inheritance (MIM 203655). We have previously mapped the gene for autosomal recessive congenital alopecia in a large inbred Pakistani family in which affected persons show complete absence of hair development (universal congenital alopecia) to a 15 cM region on chromosome 8p21-22. Here we report the cloning and characterization of the human homologue of the mouse hairless gene and show that it is located in the critical region on chromosome 8p21-22. Determining the exon-intron structure allowed detailed mutational analysis of DNA samples of patients with universal congenital alopecia. We detected a homozygous missense mutation in the Pakistani family and a homozygous splice donor mutation in a family from Oman. In addition, we show that the human hairless gene undergoes alternative splicing and that at least two isoforms generated by alternative usage of exon 17 are found in human tissues. Interestingly, the isoform containing exon 17 is the predominantly expressed isoform in all tissues but skin, where exclusive expression of the shorter isoform was observed. We speculate that this tissue-specific difference in the proportion of hairless transcripts lacking exon 17 sequences could contribute to the tissue-specific disease phenotype observed in individuals with isolated congenital alopecia.

A gene for universal congenital alopecia maps to chromosome 8p21-22

Complete or partial congenital absence of hair (congenital alopecia) may occur either in isolation or with associated defects. The majority of families with isolated congenital alopecia has been reported to follow an autosomal-recessive mode of inheritance (MIM 203655). As yet, no gene has been linked to isolated congenital alopecia, nor has linkage been established to a specific region of the genome. In an attempt to map the gene for the autosomal recessive form of the disorder, we have performed genetic linkage analysis on a large inbred Pakistani family in which affected persons show complete absence of hair development (universal congenital alopecia). We have analyzed individuals of this family, using >175 microsatellite polymorphic markers of the human genome. A maximum LOD score of 7.90 at a recombination fraction of 0 has been obtained with locus D8S258. Haplotype analysis of recombination events localized the disease to a 15-cM region between marker loci D8S261 and D8S1771. We have thus mapped the gene for this hereditary form of isolated congenital alopecia to a locus on chromosome 8p21-22 (ALUNC [alopecia universalis congenitalis]). This will aid future identification of the responsible gene, which will be extremely useful for the understanding of the biochemistry of hair development.

Human 5-HT5A receptor gene: systematic screening for DNA sequence variation and linkage mapping on chromosome 7q34-q36 using a polymorphism in the 5' untranslated region

Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter that mediates a wide range of sensory, motor, and cortical functions by activating multiple 5-HT receptor subtypes. In the present study we performed a systematic mutation scan of the complete coding region of the 5-HT5A receptor to explore its variability in the general population. Investigating 46 unrelated healthy subjects by single-strand conformation analysis no sequence changes of likely functional relevance were observed. The detection of a frequent G-->C substitution at position -19 was used for fine scale linkage mapping of the 5-HT5A gene. Employing a polymerase-chain-reaction based assay we genotyped 7 CEPH families (Centre d'Etude du Polymorphisme Humaine) and mapped the receptor to genetic markers on chromosome 7q34-q36.