Australian Pedigrees Research Articles

Evaluation of an ancestry prediction strategy for historical military remains using a World War II-era sample and pedigrees with family-level admixture

ABSTRACT Errors in ancestry prediction for historical military casework result in soldiers unable to be interred to the country they fought and died for. Australian WWII soldiers with varying degrees of European and Asian heritage are expected in the remains recovered in the Asia-Pacific, representing the greatest risk of error for Unrecovered War Casualties-Army (UWC-A). Previous research using the Ghaiyed population-specific panel (GPSP), on a modern British sample, demonstrated less variation in family-level admixture compared to four global ancestry panels. This suggested that the targeting of specific populations of interest may improve accuracy, although an evaluation using a sample of WWII-era European-Australians (W2A) with varying degrees of family-level admixture was required. This paper outlines the development of an ancestry prediction strategy using a W2A sample (non-admixed), and simulation of 4,000 genotypes representing Australian pedigrees with one Japanese ancestor (great-great-grandparent, great-grand-parent, grandparent, and parent). All great-great-grandparent to grandparent profiles were accurately predicted as W2A individuals, and although admixture at the parent level could not be resolved, no profiles were incorrectly assigned Japanese ancestry. The GPSP provided more informative predictions in contrast with the mitochondrial DNA/Y-chromosome lineage approach currently used by UWC-A as the GPSP provides an approximately 75% improvement.

Rapid Diagnosis of Spinocerebellar Ataxia 36 in a Three-Generation Family Using Short-Read Whole-Genome Sequencing Data.

Spinocerebellar ataxias are often caused by expansions of short tandem repeats. Recent methodological advances have made repeat expansion (RE) detection with whole-genome sequencing (WGS) feasible. The objective of this study was to determine the genetic basis of ataxia in a multigenerational Australian pedigree with autosomal-dominant inheritance. WGS was performed on 3 affected relatives. The sequence data were screened for known pathogenic REs using 2 RE detection tools: exSTRa and ExpansionHunter. This screen provided a clear and rapid diagnosis (<5 days from receiving the sequencing data) of spinocerebellar ataxia 36, a rare form of ataxia caused by an intronic GGCCTG RE in NOP56. The diagnosis of rare ataxias caused by REs is highly feasible and cost-effective with WGS. We propose that WGS could potentially be implemented as the frontline, cost-effective methodology for the molecular testing of individuals with a clinical diagnosis of ataxia. © 2020 International Parkinson and Movement Disorder Society.

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.

Abstract A23: Rare variants in the FAT1 gene may predispose to familial colorectal cancer

Abstract Introduction: Population- and family-based studies suggest germline predisposition in up to 35% of colorectal cancer (CRC) cases. Known genetic factors, including three highly penetrant Mendelian cancer syndromes and approximately 45 low penetrant alleles, account for less than 15% of all CRC and only a small proportion of early onset CRC. Identifying the genes responsible for the “missing” CRC predisposition will inform prevention and management. Methods: Our discovery cohort were selected to enrich for likely heritable susceptibility and consisted of 127 CRC cases from 86 pedigrees selected from Canadian and Australian CRC Family Registries (CCFRs) that met the Familial Colorectal Cancer Type X definition (satisfy Amsterdam I Criteria and lack other features of known cancer syndromes). Germline DNA from multiple CRC–affected individuals per pedigree underwent whole exome sequencing. The two replication cohorts were composed of pedigrees with multiple generations affected by CRC, one an Australian cohort of 166 families from which multiple affected and unaffected members were genotyped for rare (&amp;lt;0.01 MAF) germline likely deleterious variants in FAT1, the other a Polish cohort of 496 probands that underwent targeted next generation sequencing of FAT1. Alignment and variant calling followed the Genome Analysis Tool Kit “best practices”, and ANNOVAR was used for functional effect, allele frequency and intolerance score annotations. Variant filtering and statistical analysis were done in R (version 3.0). A hemizygous transgenic mouse model of our top genetic candidate was developed and exposed to intra-peritoneal azoxymethane (AOM) to induce colonic dysplasia. Necropsies were performed at 6 months of age, and the colons underwent gross and histologic inspection. This work was supported by grant UM1 CA167551 from the National Cancer Institute (NCI) to the Colon Cancer Family Registry. Outcomes: Using filter-based approaches in our discovery cohort, we identified rare, non-silent variants in FAT1 that co-segregated with CRC in Ontario (Canadian), Newfoundland (Canadian) and Australian pedigrees, including one stopgain variant that was found in all 4 affected of one Ontario pedigree and in 2 of 6 unaffected. Somatic loss of heterozygosity of FAT1 was seen in available FFPE tumors from 3 Ontario and 4 Australian pedigrees by either Sanger sequencing or microarray. Modified segregation analysis of genotyped multi-case families from the Australian CCFR demonstrated an overall increased risk for CRC in FAT1 carriers (HR 1.44, 95%CI 1.05-1.97), with greater hazard ratios (&amp;gt;2.5) for individual FAT1 variants identified in sufficient numbers of families. Deep sequencing in 496 Polish probands identified 4 additional rare truncating FAT1 variants. Using the ExAC database as controls, variant-level association analyses of the Polish cohort cases revealed two strongly predisposing FAT1 rare missense variants, namely c.T9440G (OR 7.53, 95%CI 4.1-12.8, Fisher's exact test, q &amp;lt; 0.05 by false discovery rates) and c.G3067A (OR 10.8, 95%CI 3.3-26.8, q &amp;lt; 0.05). Gene-level association testing was also significant for increased CRC risk when considering all rare, non-silent FAT1 variants (OR 2.2, 95%CI 1.8-2.6, q &amp;lt; 0.05). 30 FAT1 hemizygous and 28 wild type mice on a CD1 background, balanced for sex and weight, did not show differences in number or greatest size of aberrant crypts, adenoma or adenocarcinoma. Conclusions: We have shown that rare germline variants in FAT1 may predispose to CRC. Discovery of such causal genes and associated pathways will improve our understanding of early onset CRC for both familial and sporadic cases. Stratifying CRC risk by familial susceptibility genes should foster tailored, cost-effective primary and secondary prevention strategies. Citation Format: Ashton A. Connor, Jordan Lerner-Ellis, Mohammad R. Akbari, Cezary Cybulski, J Lubinski, Caroline Badouel, Helen McNeill, James G. Dowty, Mark Clendenning, Daniel D. Buchanan. Rare variants in the FAT1 gene may predispose to familial colorectal cancer. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr A23.

Unique X-linked familial FSGS with co-segregating heart block disorder is associated with a mutation in the NXF5 gene

Focal segmental glomerulosclerosis (FSGS) is the consequence of a disease process that attacks the kidney's filtering system, causing serious scarring. More than half of FSGS patients develop chronic kidney failure within 10 years, ultimately requiring dialysis or renal transplantation. There are currently several genes known to cause the hereditary forms of FSGS (ACTN4, TRPC6, CD2AP, INF2, MYO1E and NPHS2). This study involves a large, unique, multigenerational Australian pedigree in which FSGS co-segregates with progressive heart block with apparent X-linked recessive inheritance. Through a classical combined approach of linkage and haplotype analysis, we identified a 21.19 cM interval implicated on the X chromosome. We then used a whole exome sequencing approach to identify two mutated genes, NXF5 and ALG13, which are located within this linkage interval. The two mutations NXF5-R113W and ALG13-T141L segregated perfectly with the disease phenotype in the pedigree and were not found in a large healthy control cohort. Analysis using bioinformatics tools predicted the R113W mutation in the NXF5 gene to be deleterious and cellular studies support a role in the stability and localization of the protein suggesting a causative role of this mutation in these co-morbid disorders. Further studies are now required to determine the functional consequence of these novel mutations to development of FSGS and heart block in this pedigree and to determine whether these mutations have implications for more common forms of these diseases in the general population.

Familial retinal detachment associated with COL2A1 exon 2 and FZD4 mutations

To characterize the clinical and genetic abnormalities within two Australian pedigrees with high incidences of retinal detachment and visual disability. Prospective review of two extended Australian pedigrees with high rates of retinal detachment. Twenty-two family members from two extended Australian pedigrees with high rates of retinal detachment were examined. A full ophthalmic history and examination were performed, and DNA was analysed by linkage analysis and mutation screening. Characterization of a causative hereditary gene mutation in each family. All affected family members of one pedigree carried a C192A COL2A1 exon 2 mutation. None of the affected family members had early-onset arthritis, hearing abnormalities, abnormal clefting or facial features characteristic of classical Stickler syndrome. All affected members of the familial exudative vitreoretinopathy pedigree carried a 957delG FZD4 mutation. Patients with retinal detachment and a positive family history should be investigated for heritable conditions associated with retinal detachment such as Stickler syndrome and familial exudative vitreoretinopathy. The absence of non-ocular features of Stickler syndrome should raise the possibility of mutations in exon 2 of COL2A1. Similarly, late-onset familial exudative vitreoretinopathy may appear more like a rhegmatogenous detachment and not be correctly diagnosed. When a causative gene mutation is identified, cascade genetic screening of the family will facilitate genetic counselling and screening of high-risk relatives, allowing targeted management of the pre-detachment changes in affected patients.

Confirmation that Xq27 and Xq28 are susceptibility loci for migraine in independent pedigrees and a case-control cohort

Investigations into migraine genetics have suggested that susceptibility loci exist on the X chromosome. These reports are supported by evidence that demonstrates male probands as having a higher proportion of affected first-degree relatives as well as the female preponderance of 3:1 that the disorder displays. We have previously implicated the Xq24-28 locus in migraine using two independent multigenerational Australian pedigrees that demonstrated excess allele sharing at the Xq24, Xq27 and Xq28 loci. Here, we expand this work to investigate a further six independent migraine pedigrees using 11 microsatellite markers spanning the Xq27–28 region. Furthermore, 11 candidate genes are investigated in an Australian case-control cohort consisting of 500 cases and 500 controls. Microsatellite analysis showed evidence of excess allele sharing to the Xq27 marker DXS8043 (LOD* 1.38 P00.005) in MF879 whilst a second independent pedigree showed excess allele sharing to DXS8061 at Xq28 (LOD* 1.5 P00.004). Furthermore, analysis of these key markers in a case control cohort showed significant association to migraine in females at the DXS8043 marker (T1 P00.009) and association with MO at DXS8061 (T1 P00.05). Further analysis of 11 key genes across these regions showed significant association of a three-marker risk haplotype in the NSDHL gene at Xq28 (P00.0082). The results of this study add further support to the presence of migraine susceptibility loci on chromosome Xq27 and Xq28 as well as point to potential candidate genes in the regions that warrant further investigation.

A genealogical survey of Australian registered dog breeds

Breeding practices were analysed for 32 registered dog breeds representing very small registries (120 Central Asian shepherd dogs) through to very large registries (252,521 German shepherd dogs) in Australia. The vast majority (91%) of registered kennels in Australia that were sampled did not regularly employ either close breeding or popular sire usage in their kennels and the weighted mean inbreeding coefficient of Australian pedigree dogs was <5%. Australian breed mean inbreeding coefficients ranged from 0% (Central Asian shepherd dog) to 10.1% (Bichon Frise). Breed effective population sizes ranged from 26 (Ibizan hound) to 1090 (Golden retriever), comparable with other species of domesticated animals. The relatively low levels of inbreeding suggest that pedigree dog disorders are unlikely to arise frequently from the use of popular sires or close breeding in Australian registered dog breeds. It is possible that deleterious allele fixation might be driven by founder effects, genetic drift or adverse selection practices, which were not assessed in this analysis. European popular sire definitions should be revisited for rare breeds.

Positional cloning identifies SIGMAR1 gene as a causative locus for FTLD-MND in a large Australian pedigree

Positional cloning identifies SIGMAR1 gene as a causative locus for FTLD-MND in a large Australian pedigree

Apparent autosomal dominant keratoconus in a large Australian pedigree accounted for by digenic inheritance of two novel loci

Keratoconus is a debilitating ocular disease characterised by progressive asymmetrical thinning of the cornea, the clear covering at the front of the eye. The resulting protrusion of the cornea results in severe refractive error, in the most severe cases requiring corneal grafting. It is a complex disease with a genetic component. Despite several reports of linked loci, major gene identification has been elusive. A genome-wide linkage scan in a large Australian pedigree with apparent autosomal dominant keratoconus was conducted using the Affymetrix 10K SNP chip and two regions of linkage identified. Functional candidate genes from within both linkage peaks were assessed for corneal expression and screened for mutations in affected family members. Equal evidence of linkage was detected to both 1p36.23-36.21 and 8q13.1-q21.11 with LOD scores of 1.9. Analysis of both loci concurrently suggests digenic linkage with two-locus LOD score of 3.4. All affected individuals carry identical haplotypes at both loci. Carriers of either linked haplotype without the other do not have keratoconus. No mutations were identified in the following candidate genes expressed in the cornea: ENO1, CTNNBIP1, PLOD1, UBIAD1, SPSB1 or TCEB1. Although the pedigree appears to demonstrate simple autosomal dominant inheritance, the disorder is actually genetically complex. This pedigree may provide a link between inherited forms of keratoconus and sporadic cases.

Linkage studies in familial idiopathic basal ganglia calcification: Separating the wheat from the chaff

Idiopathic Basal Ganglia Calcification (IBGC) is a neuropsychiatric condition characterized by brain calcinosis, heterogeneous motor impairment and behavioral symptoms. The IBGC1 locus was the first region linked to this phenotype in an American family, but another kindred from Spain was also reported as possibly associated with this locus. Our group excluded this locus in additional families together with an independent study of an Australian pedigree with IBGC, but without clinical symptoms. Recently, a large Italian family from a population isolate was excluded from IBGC1. However, there are unusual aspects concerning this Tyrolean family, especially if we consider that almost all the clinically affected subjects manifested symptoms and signs suggestive of a dysmorphic syndrome, associated with neuropsychiatric symptoms. Curiously, some of the clinical features in this kindred match with the autosomal dominant chromosomal instability syndrome reported in Japan. Previous studies show that the definition of an autosomal dominant pattern of inheritance is an assumption that might be considered cautiously in familial IBGC, due to the limited clinical penetrance for the brain calcifications and especially when there is no access to all the parents neuroimaging data. Families from an Italian isolate, such as Tyrol, with high inbreeding rates, are more likely to manifest recessive syndromes. Nevertheless, the current debate regarding the nosology of this heterogeneous phenotype demands the establishment of standard diagnostic criteria. The current identification of loci or mutations responsible for FIBGC might help to elucidate this intriguing neuropsychiatric condition.

Screening for Glaucomatous Disc Changes Prior to Diagnosis of Glaucoma in Myocilin Pedigrees

To investigate whether structural differences of the optic nerve head are evident in young people who do not have manifest glaucoma but are known to carry myocilin mutations. A case-control design was adopted. Subjects from Australian pedigrees known to have either the Gln368STOP myocilin mutation (cutoff age, <40 years) or the Thr377Met myocilin mutation (cutoff age, <30 years) were examined for signs of glaucoma. Stereoscopic disc photographs were digitalized. Analysis of the optic disc area, optic cup area, and neuroretinal rim area was performed using digital stereoscopy with a Z-screen. Mutation analysis was conducted using direct sequencing. The t test, corrected for multiple comparison testing, was used in analysis. A total of 29 myocilin mutation-carrying (case) and 33 mutation-free (control) individuals were reviewed. The mean +/- SD ages were 19.9 +/- 9.0 and 22.1 +/- 9.5 years in the mutation and mutation-free groups, respectively (P = .35). There was no significant difference in intraocular pressure between mutation carriers and noncarriers (P = .44). There were no statistically significant differences in the mean disc, neuroretinal rim, and cup areas between the groups. The mean +/- SD neuroretinal rim area was 1.24 +/- 0.24 mm(2) in the noncarrier group and 1.25 +/- 0.23 mm(2) in the mutation group (P = .46). No notch, nerve fiber layer defect, or neuroretinal rim hemorrhage was noted in any eye examined. Although confounded by penetrance and expressivity, no quantified structural difference in the optic nerve head was observed in individuals who had a myocilin mutation prior to the diagnosis of glaucoma.

Myocilin Gly252Arg Mutation and Glaucoma of Intermediate Severity in Caucasian Individuals

To determine the phenotype of an Australian pedigree with the myocilin (MYOC) Gly252Arg mutation, comparing it with other pedigrees carrying the same mutation. All recruited subjects underwent a comprehensive clinical examination, including optic disc assessment, applanation tonometry, and visual field measurement. Mutation analysis was performed through direct sequencing. Haplotype analysis was performed using microsatellite markers around the MYOC gene. Eight Gly252Arg mutation carriers with glaucoma were identified from the same pedigree. Carriers' mean +/- SD age at diagnosis was 46.3 +/- 11.4 years (range, 31-60 years). Highest recorded intraocular pressure ranged from 27 to 42 mm Hg (mean +/- SD, 32.4 +/- 5.6 mm Hg). Cup-disc ratios in the worst eye ranged from 0.6 to 0.9. Six of the 8 individuals had undergone filtration surgery. A common founding haplotype between MY5 and D1S218 was found for Caucasian individuals tested with this mutation. One subject was compound heterozygotic for the MYOC Gly252Arg mutation and a novel MYOC Gly244Val variant. Although a common founder for Gly252Arg across Caucasian subjects was found, the phenotype from this Australian MYOC mutation-carrying pedigree is less severe than previously described. The severity of glaucoma caused by the Gly252Arg mutation may be similar to the Thr377Met MYOC mutation, yet is more severe than the most common Gln368Stop mutation. Since its implication in glaucoma, much work has been performed investigating the clinical features of MYOC-related glaucoma. Given the strong genotype-phenotype correlations with MYOC disease-causing variants, health care professionals armed with such molecular information are able to accurately counsel patients on their likely disease course. Our work suggests that the disease associated with MYOC Gly252Arg is less severe than previously described in other pedigrees with this specific mutation.

Association Study of the Dystrobrevin-Binding Gene With Schizophrenia in Australian and Indian Samples

AbstractNumerous studies have reported association between variants in the dystrobrevin binding protein 1 (dysbindin) gene (DTNBP1) and schizophrenia. However, the pattern of results is complex and to date, no specific risk marker or haplotype has been consistently identified. The number of single nucleotide polymorphisms (SNPs) tested in these studies has ranged from 5 to 20. We attempted to replicate previous findings by testing 16 SNPs in samples of 41 Australian pedigrees, 194 Australian cases and 180 controls, and 197 Indian pedigrees. No globally significant evidence for association was observed in any sample, despite power calculations indicating sufficient power to replicate several previous findings. Possible explanations for our results include sample differences in background linkage dis-equilibrium and/or risk allele effect size, the presence of multiple risk alleles upon different haplotypes, or the presence of a single risk allele upon multiple haplotypes. Some previous associations may also represent false positives. Examination of Caucasian HapMap phase II genotype data spanning theDTNBP1region indicates upwards of 40 SNPs are required to satisfactorily assess all nonredundant variation withinDTNBP1and its potential regulatory regions for association with schizophrenia. More comprehensive studies in multiple samples will be required to determine whether specificDTNBP1variants function as risk factors for schizophrenia.

Association Study of the Dystrobrevin-Binding Gene With Schizophrenia in Australian and Indian Samples

Numerous studies have reported association between variants in the dystrobrevin binding protein 1 (dysbindin) gene (DTNBP1) and schizophrenia. However, the pattern of results is complex and to date, no specific risk marker or haplotype has been consistently identified. The number of single nucleotide polymorphisms (SNPs) tested in these studies has ranged from 5 to 20. We attempted to replicate previous findings by testing 16 SNPs in samples of 41 Australian pedigrees, 194 Australian cases and 180 controls, and 197 Indian pedigrees. No globally significant evidence for association was observed in any sample, despite power calculations indicating sufficient power to replicate several previous findings. Possible explanations for our results include sample differences in background linkage disequilibrium and/or risk allele effect size, the presence of multiple risk alleles upon different haplotypes, or the presence of a single risk allele upon multiple haplotypes. Some previous associations may also represent false positives. Examination of Caucasian HapMap phase II genotype data spanning the DTNBP1 region indicates upwards of 40 SNPs are required to satisfactorily assess all nonredundant variation within DTNBP1 and its potential regulatory regions for association with schizophrenia. More comprehensive studies in multiple samples will be required to determine whether specific DTNBP1 variants function as risk factors for schizophrenia.

Identification of a novel frameshift mutation in the giant muscle filament titin in a large Australian family with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is an etiologically heterogeneous cardiac disease characterized by left ventricular dilation and systolic dysfunction. Approximately 25-30% of DCM patients show a family history of mainly autosomal dominant inheritance. We and others have previously demonstrated that mutations in the giant muscle filament titin (TTN) can cause DCM. However, the prevalence of titin mutations in familial DCM is unknown. In this paper, we report a novel heterozygous 1-bp deletion mutation (c.62890delG) in TTN that cosegregates with DCM in a large Australian pedigree (A3). The TTN deletion mutation c.62890delG causes a frameshift, thereby generating a truncated A-band titin due to a premature stop codon (p.E20963KfsX10) and the addition of ten novel amino acid residues. The clinical phenotype of DCM in kindred A3 demonstrates incomplete penetrance and variable expressivity. Finally, protein analysis of a skeletal muscle biopsy sample from an affected member did not reveal the predicted truncated titin isoform although the aberrant mRNA was present, suggesting posttranslational modification and degradation of the truncated protein. The identification of a novel disease-causing mutation in the giant titin gene in a third large family with DCM indicates that mutations in titin may account for a significant portion of the genetic etiology in familial DCM.

Confirmation of the Adult-Onset Primary Open Angle Glaucoma Locus GLC1B at 2cen-q13 in an Australian Family

Primary open-angle glaucoma (POAG) is genetically heterogeneous, with 6 named POAG loci GLC1A-F mapped and genes myocilin (MYOC) and optineurin (OPTN) identified at 2 of the loci. Using penetrance-model-free methods, we screened the POAG loci GLC1A-F in an extended Australian pedigree, using 3–5 markers within each locus. p values of less than 0.05 were obtained empirically using SimWalk2 and exactly using Genehunter for 2 markers within the GLC1B region on chromosome 2. Fine mapping of this region produced pvalues of 0.01 or less at 5 markers flanked by D2S1897 and D2S2269. The 9 cM haplotype of interest overlaps the original GLC1B region. These results provide supportive evidence for the GLC1B locus on chromosome 2cen-q13 and verify the existence of POAG susceptibility gene in this region, increasing the likelihood of gene identification.

Ratio of male to female births in the offspring of BRCA1 and BRCA2 carriers

A recent report based on 68 families, including 17 with mutations in BRCA1, suggested that there was an excess of female offspring born to BRCA1 mutation carriers. We have examined the gender ratio among offspring of 511 mutation carriers from 116 BRCA1 families, 77 and 39 from Australia and the United States, respectively. We found no evidence for a significant deviation from the expected proportion of female offspring in the Australian pedigrees, but there was an excess of female offspring in pedigrees from the USA. Ascertainment bias probably explains this bias, rather than a link with X-chromosome inactivation as previously suggested, because the families from the USA were ascertained for the purposes of linkage studies whereas those from Australia were ascertained through Familial Cancer Clinics to which they had been referred for clinical genetic counseling and mutation testing.

A genome-wide scan provides evidence for loci influencing a severe heritable form of common migraine

Migraine is a prevalent neurovascular disease with a significant genetic component. Linkage studies have so far identified migraine susceptibility loci on chromosomes 1, 4, 6, 11, 14, 19 and X. We performed a genome-wide scan of 92 Australian pedigrees phenotyped for migraine with and without aura and for a more heritable form of "severe" migraine. Multipoint non-parametric linkage analysis revealed suggestive linkage on chromosome 18p11 for the severe migraine phenotype (LOD*=2.32, P=0.0006) and chromosome 3q (LOD*=2.28, P=0.0006). Excess allele sharing was also observed at multiple different chromosomal regions, some of which overlap with, or are directly adjacent to, previously implicated migraine susceptibility regions. We have provided evidence for two loci involved in severe migraine susceptibility and conclude that dissection of the "migraine" phenotype may be helpful for identifying susceptibility genes that influence the more heritable clinical (symptom) profiles in affected pedigrees. Also, we concluded that the genetic aetiology of the common (International Headache Society) forms of the disease is probably comprised of a number of low to moderate effect susceptibility genes, perhaps acting synergistically, and this effect is not easily detected by traditional single-locus linkage analyses of large samples of affected pedigrees.

Novel ophthalmological features in hereditary endotheliopathy with retinopathy, nephropathy and stroke syndrome

The ophthalmic features are reported of a member of an Australian pedigree with three affected individuals spanning two generations with a hereditary endotheliopathy syndrome resulting in retinopathy, leukoencephalopathy and nephropathy. The index case initially presented with asymptomatic retinopathy, cerebral microvascular disease, nephropathy and raised inflammatory markers. The clinical, neuro-radiological, biochemical and histopathological findings in this patient are consistent with a diagnosis of hereditary endotheliopathy, retinopathy, nephropathy and stroke (HERNS). Linkage analysis has identified a locus for HERNS on chromosome 3p21.1-p21.3. This locus is shared with two other diseases: hereditary vascular retinopathy (HVR) and cerebroretinal vasculopathy (CRV). Although peripheral retinal involvement is a feature of HVR, it has not previously been described in HERNS. This case represents a novel phenotype of HERNS, and serves to blur the distinction between the vasculopathies mapping to chromosome 3p21. Although previously thought to be distinct clinical entities, it is possible that HERNS, HVR and CRV simply represent different phenotypes of the same disease. This will only be clarified with the identification of the gene or genes. This case also raises the question of how best to manage rare forms of vascular retinopathy.