DHPLC-based mutation analysis of ENG and ALK-1 genes in HHT Italian population

Hereditary haemorrhagic telangiectasia (HHT or Rendu-Osler-Weber syndrome) is an autosomal dominant disorder characterized by localized angiodysplasia due to mutations in endoglin, ALK-1 gene, and a still unidentified locus. The lack of highly recurrent mutations, locus heterogeneity, and the presence of mutations in almost all coding exons of the two genes makes the screening for mutations time-consuming and costly. In the present study, we developed a DHPLC-based protocol for mutation detection in ALK1 and ENG genes through retrospective analysis of known sequence variants, 20 causative mutations and 11 polymorphisms, and a prospective analysis on 47 probands with unknown mutation. Overall DHPLC analysis identified the causative mutation in 61 out 66 DNA samples (92.4%). We found 31 different mutations in the ALK1 gene, of which 15 are novel, and 20, of which 12 are novel, in the ENG gene, thus providing for the first time the mutational spectrum in a cohort of Italian HHT patients. In addition, we characterized the splicing pattern of ALK1 gene in lymphoblastoid cells, both in normal controls and in two individuals carrying a mutation in the non-invariant -3 position of the acceptor splice site upstream exon 6 (c.626-3C>G). Functional essay demonstrated the existence, also in normal individuals, of a small proportion of ALK1 alternative splicing, due to exon 5 skipping, and the presence of further aberrant splicing isoforms in the individuals carrying the c.626-3C>G mutation

Clinical and genetic analyses of three Korean families with hereditary hemorrhagic telangiectasia

<p>Abstract</p> <p>Background</p> <p>Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant vascular disorder, characterized by recurrent epistaxis, mucocutaneous telangiectases, and arteriovenous malformations (AVMs) in various visceral organs. Endoglin (<it>ENG</it>) and activin receptor-like kinase 1 (<it>ACVRL1; ALK1</it>), receptors for transforming growth factor-β (TGF-β) superfamily, have been identified as the principal HHT-causing genes.</p> <p>Methods</p> <p>Three unrelated Korean HHT patients and their asymptomatic as well as symptomatic family members were genetically diagnosed by sequencing whole exons and their flanking regions of <it>ENG </it>and <it>ACVRL1</it>. Functionality of an aberrant translation start codon, which is created by a substitution mutation at the 5'-untranslated region (UTR) of <it>ENG </it>found in a HHT family, was tested by transient <it>in vitro </it>transfection assay. Decay of the mutant transcripts was also assessed by allele-specific expression analysis.</p> <p>Results</p> <p>Two <it>ENG </it>and one <it>ACVRL1 </it>mutations were identified: a known <it>ENG </it>mutation (c.360+1G > A; p.Gly74_Tyr120del); a novel <it>ENG </it>mutation (c.1-127C > T); and a novel <it>ACVRL1 </it>mutation (c.252_253insC; p.Val85fsX168). We further validated that the 5'-UTR <it>ENG </it>mutation prevents translation of ENG from the biological translation initiation site of the mutant allele, and leads to degradation of the mutant transcripts.</p> <p>Conclusions</p> <p>This is the first experimental demonstration that a 5'-UTR mutation can prevent translation of ENG among HHT patients, and further supports the previous notion that haploinsufficiency is the primary mechanism of HHT1. Our data also underscore the importance of including exons encoding 5' UTR for HHT mutation screening.</p

Efficacy of low-dose Bevacizumab in Hereditary Hemorrhagic Telangiectasia

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New signs and old applications of echo-color-Doppler should always be compared to a gold standard

In our previous study, we described a new Doppler sign, called ‘color-spot’, particularly suitable for identifying small hepatic arterio-venous malformations (HAVMs) and verified its accuracy using multislice CT (MSCT) as gold standard. Moreover, we clearly distinguished the color-spots found in the peripheral subcapsular region of the liver from ‘hepatic hypervascularization’, a sign previously reported by Caselitz et al.. Both are suggestive of small HAVMs and provide a greater diagnostic sensitivity for HAVMs in HHT when compared to previously published extrahepatic parameter

Formation of renal cystis in patients with Hereditary Haemorrhagic Telangiectasia

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Capillaroscopy of the dorsal skin of the hands in hereditary hemorrhagic telangiectasia

Background: Cutaneous telangiectases are manifestations of hereditary hemorrhagic telangiectasia (HHT), a dominantly inherited disorder. Telangiectases have been studied by skin biopsy, and recently by nailfold capillaroscopy. Aim: To confirm the diagnostic role of nailfold capillaroscopy, and assess the value of skin capillaroscopy of the dorsum of the hands in HHT. Design: Prospective clinical investigation. Methods: Using a Wild Heerbrugg-M650 microscope, we studied the nailfolds and dorsum of the hands of 88 patients (37 females, 51 males, mean age 39.7 +/- 18.4 years), including 85 with positive genetic testing and three with clinical diagnosis (at least three clinical criteria but a negative genetic test) and 27 controls (13 females, 14 males, mean age 38.6 +/- 19.6 years). Results: Microscopic telangiectases were observed on the dorsum of the hands in 80/88 patients (91%): 77 with positive and three with negative genetic tests. No control showed vascular abnormalities. In six patients (7%), nailfold capillaroscopy showed pseudo-megacapillaries and megacapillaries; the remaining 82 (93%) and all controls, had normal capillaroscopic patterns. Discussion: HHT can induce morphological changes in microcirculation that are more easily detectable on the dorsum of the hands than in the nailfold. Microscopic lesions without macroscopic telangiectases were also noted, suggesting the need for further research. Capillaroscopy may provide an additional non-invasive diagnostic criterion for HHT

Endoglin gene mutations and polymorphisms in Italian patients with hereditary haemorrhagic telangiectasia

Autosomal-dominant hereditary haemorrhagic telangiectasia (HHT) is a genetically heterogeneous disease caused by mutations in at least two different loci. We screened for mutations in four Italian families where segregation studies showed clear evidence of linkage to the endoglin (ENG ) locus. In addition, one sporadic case and three patients with pulmonary arteriovenous malformations, belonging to small nuclear families unsuitable for linkage analysis, were included in the screening. The proband from each family was investigated using single-strand conformation polymorphism and heteroduplex analysis; potential variants were sequenced. Four novel and one previously reported mutation were detected, as well as three new polymorphisms. The novel mutations included deletions in exon 1 (patient 581/02), exon 5 (patient 780/01) and exon 7 (patient 700/01), and a C-->T229 substitution in exon 3 (patient 462/02). When analysing patient 700/01 and his affected daughter, we encountered a mutant ENG allele with two mutations - a deletion in exon 7 and a substitution in exon 12 - which converts isoleucine 575 into threonine, in a non-conserved region. Both mutations were absent in the two healthy sons of the patient, while the polymorphic variant in exon 12 was present in his healthy father. These results and haplotype-segregation studies suggest that a de novo deletion had occurred in the gamete of paternal origin. For the first time the parental germline in which a de novo HHT mutation occurred has been identified