Absence of association of asporin polymorphisms and osteoarthritis susceptibility in US Caucasians.

OBJECTIVE: An association between osteoarthritis (OA) and functional polymorphisms in the aspartic acid (d) repeat of the asporin (ASPN) gene was reported in Japanese and Han Chinese populations. The aim of this study was to assess the association of variants in the ASPN gene with the presence of radiographic hand and/or knee OA in a US Caucasian population. METHODS: Ten single nucleotide polymorphisms (SNPs) within the ASPN gene were genotyped in 775 affected siblings with radiographically confirmed hand and/or knee OA, and the allelic, genotypic and haplotypic association results were examined. RESULTS: One variant (SNP RS7033979) showed nominal evidence of association with both hand OA (P=0.042) and knee OA (P=0.032). Four additional SNPs showed nominal evidence of association with knee OA only. These associations were only observed with genotypic tests; the corresponding allelic and haplotype tests did not corroborate the single-point association results. CONCLUSION: These data suggest that polymorphisms within ASPN are not a major influence in susceptibility to hand or knee OA in US Caucasians.

The Genetics of Generalized Osteoarthritis (GOGO) study: study design and evaluation of osteoarthritis phenotypes.

PURPOSE: The primary goal of the Genetics of Generalized Osteoarthritis (GOGO) study is to identify chromosomal regions associated with increased susceptibility to generalized osteoarthritis (OA). Here we describe the study design and phenotype of the 2728 participants from the 1145 families recruited for this study. METHODS: GOGO is an investigator-initiated collaboration involving seven clinical academic sites and sponsored by GlaxoSmithKline. Family ascertainment was carried out between 1999 and 2002. A qualifying family required self-reported Caucasian ethnicity and at least two affected siblings with clinical hand OA. We hypothesized that this clinical phenotype would facilitate identification of participants with multijoint radiographic OA (rOA) in and beyond the hand. The "gold standard" case definition, however, was based on rOA (Kellgren-Lawrence grade > or =2) involving > or =3 hand joints distributed bilaterally and including at least one distal interphalangeal joint, with two of the three involved joints within a joint group (distal interphalangeal, proximal interphalangeal, or carpometacarpal). Radiographs of hips, knees and spine were also obtained. Additional siblings and living parents from qualifying families, both affected and unaffected, were invited to participate. RESULTS: A total of 2706 participants had complete clinical and radiological examination data. Of these, 2569 participants met clinical examination criteria for affected status; while 1963 (73%) participants met the prespecified radiographic criteria for affected status. This corresponded to a total of 707 families with at least two affected siblings that met the hand rOA criteria. Of those individuals with rOA of the hand, the frequency of rOA at other sites was highest for the knee (51%) and spine (54%), and less common for the hip (25%). Concordance rates among hand affected siblings were greatest for spine (36%) followed by knee (31%) and hip (9%); a total of 53% of the affected sib pairs were concordant for specific patterns of generalized rOA involving the hand and large joints (knees, hips or spine). CONCLUSIONS: GOGO represents a large multicenter collection of families with multiple joint OA that have been characterized both clinically and radiographically. The GOGO study will employ a comprehensive strategy for genetic screening based upon both qualitative and quantitative radiographic trait analyses, circulating biomarkers in a quantitative trait-based analysis, fine mapping, and candidate gene analysis. This sample should provide sufficient power to detect linkage to OA associated genes.

A strategy for primary high throughput cytotoxicity screening in pharmaceutical toxicology.

PURPOSE: Recent advances in combinatorial chemistry and high throughput screens for pharmacologic activity have created an increasing demand for in vitro high throughput screens for toxicological evaluation in the early phases of drug discovery. METHODS: To develop a strategy for such a screen, we have conducted a data mining study of the National Cancer Institute's Developmental Therapeutics Program (DTP) cytotoxicity database. RESULTS: Using hierarchical cluster analysis, we confirmed that the different tissues of origin and individual cell lines showed differential sensitivity to compounds in the DTP Standard Agents database. Surprisingly, however, approaching the data globally, linear regression analysis showed that the differences were relatively minor. Comparison with the literature on acute toxicity in mice showed that the predictive power of growth inhibition was marginally superior to that of cell death. CONCLUSIONS: This datamining study suggests that in designing a strategy for high throughput cytotoxicity screening: a single cell line, the choice of which may not be critical, can be used as a primary screen; a single end point may be an adequate measure and a cut off value for 50% growth inhibition between 10(-6) and 10(-8) M may be a reasonable starting point for accepting a cytotoxic compound for scale up and further study.

Identification of a novel transcript disrupted by a balanced translocation associated with DiGeorge syndrome.

Most cases of DiGeorge syndrome (DGS) and related abnormalities are associated with deletions within 22q11. Shortest region of deletion overlap (SRO) mapping previously identified a critical region (the DGCR) of 500 kb, which was presumed to contain a gene or genes of major effect in the haploinsufficiency syndromes. The DGCR also contains sequences disrupted by a balanced translocation that is associated with DGS--the ADU breakpoint. We have cloned sequences at the breakpoint and screened for novel genes in its vicinity. A series of alternatively spliced transcripts expressed during human and murine embryogenesis, but with no obvious protein encoding potential, were identified. The gene encoding these RNAs has been named DGCR5 and it is disrupted by the patient ADU breakpoint. DGCR5 is distinct from the DGCR3 open reading frame (ORF) previously shown to be interrupted by the ADU translocation, although DGCR3 is embedded within a DGCR5 intron and in the same (predicted) transcriptional orientation. No mutations of DGCR5 have yet been detected. By analogy to other loci encoding conserved, nontranslated RNAs, it is possible that DGCR5 originates from a cis-acting transcriptional control element in the vicinity of the ADU/VDU breakpoint. Disruption of such an element would result in altered transcription of neighboring genes secondary to a position effect, a hypothesis in keeping with recent refinement of the SRO placing the ADU breakpoint outside the DGCR.

Isolation of a gene encoding an integral membrane protein from the vicinity of a balanced translocation breakpoint associated with DiGeorge syndrome.

Deletions within 22q11 have been associated with a wide variety of birth defects embraced by the acronym CATCH22 and including the DiGeorge syndrome, Shprintzen syndrome (velocardiofacial syndrome) and congenital heart disease. It is not known how many genes contribute to this phenotype. Previous studies have shown that a balanced translocation disrupts sequences within the shortest region of deletion overlap for DiGeorge syndrome. A P1 clone was isolated which spans this breakpoint and used to isolate a cDNA encoding a transmembrane protein expressed in a wide variety of tissues. This gene (called IDD) is not disrupted by the translocation, but maps within 10 kb of the breakpoint. Mutation analysis of five affected cases with no previously identified chromosome 22 deletion was negative, but a potential protein polymorphism was discovered. No deletions or rearrangements were detected in these patients following analysis with markers closely flanking the breakpoint, data which emphasize that large (i.e. over 1 Mb) interstitial deletions are the rule in DiGeorge syndrome. The proximity of IDD to the balanced translocation breakpoint and its position within the shortest region of deletion overlap indicate that this gene may have a role, along with other genes, in the CATCH22 haploinsufficiency syndromes.

Exclusion of chromosome 6 and 8 locations in nonrhodopsin autosomal dominant retinitis pigmentosa families: further locus heterogeneity in adRP.

Genetic studies have revealed that 25 to 30% of autosomal dominant retinitis pigmentosa (adRP) families have mutations in the rhodopsin gene, while the remainder do not. More recently linkage data and mutation detection have demonstrated two further loci implicated in adRP, at an as yet unidentified gene on chromosome 8p and at the human gene homologue of the mouse Rds (Retinal Degeneration Slow) gene on chromosome 6p. We have previously reported exclusion of adRP from the rhodopsin locus on 3q in two large adRP families. We now report exclusion data for both families, on chromosomes 6 and 8, demonstrating that the adRP phenotype results from mutations in at least four locations.

Recombination between rhodopsin and locus D3S47 (C17) in rhodopsin retinitis pigmentosa families.

Autosomal dominant retinitis pigmentosa (adRP) has shown linkage to the chromosome 3q marker C17 (D3S47) in two large adRP pedigrees known as TCDM1 and adRP3. On the basis of this evidence the rhodopsin gene, which also maps to 3q, was screened for mutations which segregated with the disease in adRP patients, and several have now been identified. However, we report that, as yet, no rhodopsin mutation has been found in the families first linked to C17. Since no highly informative marker system is available in the rhodopsin gene, it has not been possible to measure the genetic distance between rhodopsin and D3S47 accurately. We now present a linkage analysis between D3S47 and the rhodopsin locus (RHO) in five proven rhodopsin-retinitis pigmentosa (rhodopsin-RP) families, using the causative mutations as highly informative polymorphic markers. The distance, between RHO and D3S47, obtained by this analysis is theta = .12, with a lod score of 4.5. This contrast with peak lod scores between D3S47 and adRP of 6.1 at theta = .05 and 16.5 at theta = 0 in families adRP3 and TCDM1, respectively. These data would be consistent with the hypothesis that TCDM1 and ADRP3 represent a second adRP locus on chromosome 3q, closer to D3S47 than is the rhodopsin locus. This result shows that care must be taken when interpreting adRP exclusion data generated with probe C17 and that it is probably not a suitable marker for predictive genetic testing in all chromosome 3q-linked adRP families.