Birgit Carlsson

The gene encoding ribosomal protein S19 is mutated in Diamond-Blackfan anaemia

Diamond–Blackfan anaemia (DBA) is a constitutional erythroblastopenia characterized by absent or decreased erythroid precursors. The disease, previously mapped to human chromosome 19q13, is frequently associated with a variety of malformations. To identify the gene involved in DBA, we cloned the chromosome 19q13 breakpoint in a patient with a reciprocal X;19 chromosome translocation. The breakpoint occurred in the gene encoding ribosomal protein S19. Furthermore, we identified mutations in RPS19 in 10 of 40 unrelated DBA patients, including nonsense, frameshift, splice site and missense mutations, as well as two intragenic deletions. These mutations are associated with clinical features that suggest a function for RPS19 in erythropoiesis and embryogenesis.

Loss of ZDHHC15 expression in a woman with a balanced translocation t(X;15)(q13.3;cen) and severe mental retardation.

X-linked mental retardation (XLMR) affects one in 600 males and is highly heterogeneous. We describe here a 29-year-old woman with severe nonsyndromic mental retardation and a balanced reciprocal translocation between chromosomes X and 15 [46,XX,t(X;15)(q13.3;cen)]. Methylation studies showed a 100% skewed X-inactivation in patient-derived lymphocytes indicating that the normal chromosome X is retained inactive. Physical mapping of the breakpoints localised the Xq13.3 breakpoint to within 3.9 kb of the first exon of the ZDHHC15 gene encoding a zinc-finger and a DHHC domain containing product. Expression analysis revealed that different transcript variants of the gene are expressed in brain. ZDHHC15-specific RT-PCR analysis on lymphocytes from the patient revealed an absence of ZDHHC15 transcript variants, detected in control samples. We suggest that the absence of the ZDHHC15 transcripts in this patient contributes to her phenotype, and that the gene is a strong candidate for nonsyndromic XLMR.

Alterations in the expression, structure and function of progesterone receptor membrane component-1 (PGRMC1) in premature ovarian failure

Premature ovarian failure (POF) is characterized by hypergonadotropic hypogonadism and amenorrhea before the age of 40. The condition has a heterogeneous background but genetic factors are demonstrated by the occurrence of familial cases. We identified a mother and daughter with POF both of whom carry an X;autosome translocation [t(X;11)(q24;q13)]. RNA expression studies of genes flanking the X-chromosome breakpoint revealed that both patients have reduced expression levels of the gene Progesterone Receptor Membrane Component-1 (PGRMC1). Mutation screening of 67 females with idiopathic POF identified a third patient with a missense mutation (H165R) located in the cytochrome b5 domain of PGRMC1. PGRMC1 mediates the anti-apoptotic action of progesterone in ovarian cells and it acts as a positive regulator of several cytochrome P450 (CYP)-catalyzed reactions. The CYPs are critical for intracellular sterol metabolism, including biosynthesis of steroid hormones. We show that the H165R mutation associated with POF abolishes the binding of cytochrome P450 7A1 (CYP7A1) to PGRMC1. In addition, the missense mutation attenuates PGRMC1s ability to mediate the anti-apoptotic action of progesterone in ovarian cells. These findings suggest that mutant or reduced levels of PGMRC1 may cause POF through impaired activation of the microsomal cytochrome P450 and increased apoptosis of ovarian cells.

Constitutional downregulation of SEMA5A expression in autism

There is strong evidence for the importance of genetic factors in idiopathic autism. The results from independent twin and family studies suggest that the disorder is caused by the action of several genes, possibly acting epistatically. We have used cDNA microarray technology for the identification of constitutional changes in the gene expression profile associated with idiopathic autism. Samples were obtained and analyzed from 6 affected subjects belonging to multiplex autism families and from 6 healthy controls. We assessed the expression levels for approximately 7,700 genes by cDNA microarrays using mRNA derived from Epstein-Barr virus-transformed B lymphocytes. The microarray data were analyzed in order to identify up- or downregulation of specific genes. A common pattern with nine downregulated genes was identified among samples derived from individuals with autism when compared to controls. Four of these nine genes encode proteins involved in biological processes associated with brain function or the immune system, and are consequently considered as candidates for genes associated with autism. Quantitative real-time PCR confirms the downregulation of the gene encoding SEMA5A, a protein involved in axonal guidance. Epstein-Barr virus should be considered as a possible source for altered expression, but our consistent results make us suggest SEMA5A as a candidate gene in the etiology of idiopathic autism.

The binding of chondroitin sulphate to collagen

The binding of connective tissue polysaccharides to collagen has been the subject of a number of investigations most recently by one of us [ 1,2 j . By means of light-scattering it could be shown that at physiological pH and ionic strength, there is a weak interaction between collagen and chondroitin 4-sulphate and that only a limited number of polysaccharide molecules could bind to each collagen molecule [2j . In the present communication we have investigated the binding of chondroitin sulphate to collagen which was coupled covalently to agarose beads. The use of collagen-substituted agarose gels in interaction studies with glycosaminoglycans has been reported earlier by us [3] and most recently by Greenwald et al. [4]. With this technique, experiments may be performed over a large range of ionic strengths in spite of the low solubility of collagen at low salt concentrations and neutral pH. We have found that there are at least three binding sites for chondroitin 4-sulphate on each collagen. The number of sites is constant but the binding affinity decreases with increasing ionic strength.

Assignment of the locus for ichthyosis prematurity syndrome to chromosome 9q33.3–34.13

Autosomal recessive congenital ichthyosis (ARCI) is a clinically and genetically heterogeneous group of inherited disorders of keratinisation, with an estimated incidence of one per 200 000 newborns.1 In Scandinavia, the prevalence is closer to one in 50 000.2,3 By electron microscopy, ARCI can be classified into four subgroups—ichthyosis congenita I–IV—and one so far undefined group. Six loci have been associated with ARCI: on chromosomes 2q34 (LI2 (MIM 601277)), 3p21 (NCIE2 (MIM 604780)), 14q11.2 (LI1 (MIM 242300) and NCIE1 (MIM 242100)), 17p13.1 (LI5 (MIM 606545)), 19p12–q12 (LI3 (MIM 190195)), and 19p13.1–p13.2 (NNCI (MIM 604781)).4–9 Genes that correspond to four of these have been identified: the transglutaminase 1 gene ( TGM1 (MIM 190195)) on chromosome 14q11, the comparative gene identification 58 ( CGI-58 (MIM 604780)) on chromosome 3p21, two genes from the lipoxygenase (LOX) family—lipoxygenase-3 ( ALOX3 ) and 12(R)-lipoxygenase ( ALOX12B (MIM 603741))—on chromosome 17p13.1, and, most recently, the adenosine triphosphate binding cassette 12A ( ABCA12A (MIM 607800)) on chromosome 2q34.10–14 The transglutaminase 1 protein takes part in the formation of the lipid envelope on the surface of epidermal keratinocytes. Cells with a disrupted TGM1 gene have a defective epidermal barrier function. TGM1 is altered in one third of patients with ichthyosis congenita type I and all patients with ichthyosis congenita type II.2,12,15,16 Mutations in the CGI-58 gene on chromosome 3p21 cause Chanarin-Dorfman disease (CDS (MIM 275630)). The protein CGI-58 belongs to a large family of proteins characterised by an α/β hydrolase fold and contains three sequence motifs found in the esterase, lipase, and thioesterase subfamily. Affected patients have raised levels of triacylglycerol, and CGI-58 has been postulated to be involved in recycling of triacylglycerol derived monoacylglycerol or diacylglycerol to specific phospholipids or in the catabolism of long chain fatty acids.11 Mutations in either of …

A candidate region for Asperger syndrome defined by two 17p breakpoints

Asperger syndrome (AS) is a mild form of autistic disorder characterised by impairment in social interaction as well as a restricted pattern of behaviour, interests, and activities. Two patients with AS and balanced translocations t(13;17) and t(17;19), respectively, were identified. Fluorescent in situ hybridisation (FISH) analysis with chromosome 17 specific clones to metaphase chromosomes from both patients showed that the chromosome 17 breakpoints are located within a 300 kb region at 17p13. The region spans 14 known genes. The expression of these genes was analysed in lymphoblastoid RNA derived from the patients and healthy control individuals. The CHRNE, DKFZP566H073, LOC90048, PFN1, SPAG7, KIAA0909, ZNF232 and KIF1C genes showed similar levels of expression in cell lines with the translocations when compared with cell lines with normal karyotype. No expression was detected for the MINK, GP1BA, SLC25A11, ENO3, FLJ10060 and USP6 genes in any of the cell lines. The close physical relation of the two 17p breakpoints suggest a common genetic aetiology for the phenotype in the patients. Structural and functional analysis of the genes located around the two 17p breakpoints in t(13;17) and t(17;19) patients may reveal candidate sequences for the AS phenotype.

RAR-related orphan receptor A isoform 1 (RORa1) is disrupted by a balanced translocation t(4;15)(q22.3;q21.3) associated with severe obesity.

We have identified a family comprising a mother and two children with idiopathic and profound obesity body mass index (BMI) 41–49 kg/m2. The three family members carry a balanced reciprocal chromosome translocation t(4;15). We present here the clinical features of the affected individuals as well as the physical mapping and cloning of the chromosomal breakpoints. A detailed characterisation of the chromosomal breakpoints at chromosomes 4 and 15 revealed that the translocation is almost perfectly balanced with a very short insertion/deletion. The chromosome 15 breakpoint is positioned in intron 1 of the RAR-related orphan receptor A isoform 1 (RORa1) and the chromosome 4 breakpoint is positioned 133 kb telomeric to the transcriptional start of the unc-5 homolog B (UNC5C) and 154 kb centromeric of the transcriptional start of the pyruvate dehydrogenase (lipoamide) alpha 2 (PDHA2). The rearrangement creates a fusion gene, which includes the RORa1 exon 1 and UNC5C that is expressed in frame in adipocytes from the affected patients. We also show that this transcript is translated into a protein. From previous reports, it is shown that RORa1 is implicated in the regulation of adipogenesis and lipoprotein metabolism. We hypothesise that the obesity in this family is caused by (i) haploinsufficiency for RORa1 or, (ii) a gain of function mechanism mediated by the RORa1–UNC5C fusion gene.

Physical chemical characterization of percoll. II. Size and interaction of colloidal particles

Abstract The particle size of Percoll, a polyvinylpyrrolidone-coated colloidal silica, has been analyzed by various techniques. The mean diameter of the dry particle from electron microscopy and from the molecular weight and partial specific volume is 21–22 nm. Hydrodynamic measurements (viscometry and sedimentation) give values of 29–30 and 35 nm in 0.15 M NaCl and water, respectively, indicating a layer of hydration on the particles which is more pronounced at low ionic strength. The second virial coefficient for Percoll in 0.15 M NaCl, as estimated from light scattering, osmometry, and sedimentation equilibrium, was 1.3–2.9 × 10 −6 . Assuming excluded volume to be the origin of the second virial coefficient one can calculate an effective particle diameter of 35–46 nm which is larger than the measured hydrodynamic diameter. Electrostatic forces do apparently contribute to the exclusion. The second virial coefficient in water is 100-fold larger than in 0.15 M NaCl. In the course of this investigation a technique was designed to measure sedimentation equilibria of concentrated Percoll solutions in a preparative zonal rotor. The colloid was concentrated in the bottom fraction of one run to 0.58 g/ml which is close to tight packing of the hydrated spheres. The material was still a clear fluid and no precipitate or gel was noticed during a long observation period.

A chromosome 10 variant with a 12 Mb inversion [inv(10)(q11.22q21.1)] identical by descent and frequent in the Swedish population

We identified a paracentric inversion of chromosome 10 [inv(10)(q11.22q21.1)] in 0.20% of Swedish individuals (15/7,439) referred for cytogenetic analysis. A retrospective analysis of 8,896 karyotypes from amniocenteses in Sweden revealed a carrier frequency of 0.079% (7/8,896) for the inversion. Cloning and detailed analysis of the inversion breakpoint regions show enrichment for interspersed repeat elements and AT‐stretches. The centromeric breakpoint coincides with that of a predicted inversion from HapMap data, which suggests that this region is involved in several chromosome 10 variants. No known gene or predicted transcript are disrupted by the inversion which spans approximately 12 Mb. Carriers from four non‐related Swedish families have identical inversion breakpoints and haplotype analysis confirmed that the rearrangement is identical by descent. Diagnosis was retrieved in 6 out of the 15 carriers referred for cytogenetic analysis. No consistent phenotype was found to be associated with the inversion. Our study demonstrates that the inv(10)(q11.22q21.1) is a rare and inherited chromosome variant with a broad geographical distribution in Sweden.