Noncoding Variations in the Gene Encoding Ceramide Synthase 6 are Associated with Type 2 Diabetes in a Large Indigenous Australian Pedigree.

Type 2 diabetes (T2D) is a chronic disease that disproportionately affects Indigenous Australians. We have previously reported the localization of a novel T2D locus by linkage analysis to chromosome 2q24 in a large admixed Indigenous Australian pedigree (Busfield et al. (2002). American Journal of Human Genetics, 70, 349-357). Here we describe fine mapping of this region in this pedigree, with the identification of SNPs showing strong association with T2D: rs3845724 (diabetes p = 7 × 10-4), rs4668106 (diabetes p = 9 × 10-4) and rs529002 (plasma glucose p = 3 × 10-4). These associations were successfully replicated in an independent collection of Indigenous Australian T2D cases and controls. These SNPs all lie within the gene encoding ceramide synthase 6 (CERS6) and thus may regulate ceramide synthesis.

Observation of a novel Babesia spp. in Eastern Grey Kangaroos (Macropus giganteus) in Australia.

The roles and epidemiological features of tick-borne protozoans are not well elicited in wildlife. Babesia spp. are documented in many domestic animals, including cattle, horses, pigs, dogs and cats. Three cases affecting eastern grey kangaroos are described. The kangaroos exhibited neurological signs, depression and marked anaemia, and microscopic examination of blood smears revealed intraerythrocytic piroplasms. One to seven intraerythrocytic spherical, oval, pyriform and irregularly-shaped parasites consistent with Babesia spp. were seen in the blood smears and the percentage of infected erythrocytes was estimated to be approximately 7% in each case. Data suggest that the tick vector for this kangaroo Babesia sp. is a Haemaphysalis species. For Case 2, ultrastructural examination of the erythrocytes of the renal capillaries showed parasites resembling Babesia spp. and 18 of 33 erythrocytes were infected. DNA sequencing of the amplified 18S rDNA confirmed that the observed intraerythrocytic piroplasms belong to the genus Babesia. The phylogenetic position of this new kangaroo Babesia sp. (de novo Babesia macropus), as a sister species to the new Australian woylie Babesia sp., suggests a close affinity to the described Afro-Eurasian species Babesia orientalis and Babesia occultans suggesting perhaps a common ancestor for the Babesia in kangaroos.

Carotid artery intimal medial thickness, brachial artery flow-mediated vasodilation and cardiovascular risk factors in diabetic and non-diabetic indigenous Australians.

BACKGROUND: Indigenous Australians are at high risk for cardiovascular disease and type 2 diabetes. Carotid artery intimal medial thickness (CIMT) and brachial artery flow-mediated vasodilation (FMD) are ultrasound imaging based surrogate markers of cardiovascular risk. This study examines the relative contributions of traditional cardiovascular risk factors on CIMT and FMD in adult Indigenous Australians with and without type 2 diabetes mellitus. METHOD: One hundred and nineteen Indigenous Australians were recruited. Physical and biochemical markers of cardiovascular risk, together with CIMT and FMD were measured for all subjects. RESULTS: Fifty-three Indigenous Australians subjects (45%) had type 2 diabetes mellitus. There was a significantly greater mean CIMT in diabetic versus non-diabetic subjects (p=0.049). In the non-diabetic group with non-parametric analyses, there were significant correlations between CIMT and: age (r=0.64, p<0.001), systolic blood pressure (r=0.47, p<0.001) and non-smokers (r=-0.30, p=0.018). In the diabetic group, non-parametric analysis showed correlations between CIMT, age (r=0.36, p=0.009) and duration of diabetes (r=0.30, p=0.035) only. Adjusting for age, sex, smoking and history of cardiovascular disease, Hb(A1c) became the sole significant correlate of CIMT (r=0.35, p=0.01) in the diabetic group. In non-parametric analysis, age was the sole significant correlate of FMD (r=-0.31, p=0.013), and only in non-diabetic subjects. Linear regression analysis showed significant associations between CIMT and age (t=4.6, p<0.001), systolic blood pressure (t=2.6, p=0.010) and Hb(A1c) (t=2.6, p=0.012), smoking (t=2.1, p=0.04) and fasting LDL-cholesterol (t=2.1, p=0.04). There were no significant associations between FMD and examined cardiovascular risk factors with linear regression analysis CONCLUSIONS: CIMT appears to be a useful surrogate marker of cardiovascular risk in this sample of Indigenous Australian subjects, correlating better than FMD with established cardiovascular risk factors. A lifestyle intervention programme may alleviate the burden of cardiovascular disease in Indigenous Australians by reducing central obesity, lowering blood pressure, correcting dyslipidaemia and improving glycaemic control. CIMT may prove to be a useful tool to assess efficacy of such an intervention programme.

Identification of SQSTM1 mutations in familial Paget's disease in Australian pedigrees.

We have conducted a genome-wide scan on a pedigree containing 372 adult members, of whom 49 have PDB. In the present study, we report linkage of a large pedigree to the PDB3 region on chromosome 5q35-qter with a peak multipoint LOD score of 6.77. Sequestosome 1 (SQSTM/p62) has been identified as the causative PDB gene in this region. Six sequestosome 1 mutations have been described to date. Four mutations have been identified in exon 8, 1210delT and 1215delC both resulting in premature stop codon at amino acid 394, 1215C to T (P392L), 1224insT (E396X), one mutation in exon 7, 1200C to T (P387L) and a G to A splice junction mutation at IVS7+1. These mutations cluster in the C terminus of the protein and are predicted to disrupt the ubiquitin binding properties of sequestosome 1. Sequence analysis of the gene encoding sequestosome 1 revealed a single base pair deletion (1215delC) segregating with the majority of affected members in the pedigree. This deletion introduces a stop codon at position 394, resulting in premature termination of the protein (L394X) and loss of the ubiquitin-associated binding domain. Screening of affected members from 10 further PDB families identified the previously reported P392L mutation in one family. No SQSTM1/p62 coding mutations were found in the remaining 9 families or in 113 age-matched controls.

Linkage of Paget disease of bone to a novel region on human chromosome 18q23.

Paget disease of bone (PDB) is characterized by increased osteoclast activity and localized abnormal bone remodeling. PDB has a significant genetic component, with evidence of linkage to chromosomes 6p21.3 (PDB1) and 18q21-22 (PDB2) in some pedigrees. There is evidence of genetic heterogeneity, with other pedigrees showing negative linkage to these regions. TNFRSF11A, a gene that is essential for osteoclast formation and that encodes receptor activator of nuclear factor-kappa B (RANK), has been mapped to the PDB2 region. TNFRSF11A mutations that segregate in pedigrees with either familial expansile osteolysis or familial PDB have been identified; however, linkage studies and mutation screening have excluded the involvement of RANK in the majority of patients with PDB. We have excluded linkage, both to PDB1 and to PDB2, in a large multigenerational pedigree with multiple family members affected by PDB. We have conducted a genomewide scan of this pedigree, followed by fine mapping and multipoint analysis in regions of interest. The peak two-point LOD scores from the genomewide scan were 2.75, at D7S507, and 1.76, at D18S70. Multipoint and haplotype analysis of markers flanking D7S507 did not support linkage to this region. Haplotype analysis of markers flanking D18S70 demonstrated a haplotype segregating with PDB in a large subpedigree. This subpedigree had a significantly lower age at diagnosis than the rest of the pedigree (51.2+/-8.5 vs. 64.2+/-9.7 years; P=.0012). Linkage analysis of this subpedigree demonstrated a peak two-point LOD score of 4.23, at marker D18S1390 (straight theta=0), and a peak multipoint LOD score of 4.71, at marker D18S70. Our data are consistent with genetic heterogeneity within the pedigree and indicate that 18q23 harbors a novel susceptibility gene for PDB.

A genomewide search for type 2 diabetes-susceptibility genes in indigenous Australians.

The prevalence of type 2 diabetes among Australian residents is 7.5%; however, prevalence rates up to six times higher have been reported for indigenous Australian communities. Epidemiological evidence implicates genetic factors in the susceptibility of indigenous Australians to type 2 diabetes and supports the hypothesis of the "thrifty genotype," but, to date, the nature of the genetic predisposition is unknown. We have ascertained clinical details from a community of indigenous Australian descent in North Stradbroke Island, Queensland. In this population, the phenotype is characterized by severe insulin resistance. We have conducted a genomewide scan, at an average resolution of 10 cM, for type 2 diabetes-susceptibility genes in a large multigeneration pedigree from this community. Parametric linkage analysis undertaken using FASTLINK version 4.1p yielded a maximum two-point LOD score of +2.97 at marker D2S2345. Multipoint analysis yielded a peak LOD score of +3.9 <1 cM from marker D2S2345, with an 18-cM 3-LOD support interval. Secondary peak LOD scores were noted on chromosome 3 (+1.8 at recombination fraction [theta] 0.05, at marker D3S1311) and chromosome 8 (+1.77 at theta=0.0, at marker D8S549). These chromosomal regions are likely to harbor novel susceptibility genes for type 2 diabetes in the indigenous Australian population.