Long-term follow-up of patients with popliteal artery entrapment syndrome treated by endoluminal revascularization

The popliteal artery entrapment syndrome (PAES), a rare cause for leg ischemia, is usually treated by surgical removal of the compressing structure and either venous bypass or interposition graft. However, endovascular revascularization followed by surgery to release the artery has been reported as a feasible alternative. So far long-term results of this approach are not known. We report the follow-up of three patients with PAES and thrombotic occlusion of the popliteal and calf arteries treated by local lysis, percutaneous thrombembolectomy and angioplasty followed by musculotendinous dissection. One patient had an uneventful follow-up of 11 years while the second patient developed a popliteal aneurysm four months after the index procedure. In the third patient, angioplasty of a stenosis of the popliteal artery was performed after two years. However, occlusion of the artery occurred two years later due to a small popliteal aneurysm. Endovascular revascularization followed by surgical release of the artery may be a viable alternative in the treatment of PAES especially in cases with distal embolization. However, careful follow-up by duplex ultrasound is mandatory because of the high risk of reocclusion or development of a popliteal aneurysm.

A novel DFNB1 deletion allele supports the existence of a distant cis-regulatory region that controls GJB2 and GJB6 expression

Eleven affected members of a large German-American family segregating recessively inherited, congenital, non-syndromic sensorineural hearing loss (SNHL) were found to be homozygous for the common 35delG mutation of GJB2, the gene encoding the gap junction protein Connexin 26. Surprisingly, four additional family members with bilateral profound SNHL carried only a single 35delG mutation. Previously, we demonstrated reduced expression of both GJB2 and GJB6 mRNA from the allele carried in trans with that bearing the 35delG mutation in these four persons. Using array comparative genome hybridization (array CGH), we have now identified on this allele a deletion of 131.4 kb whose proximal breakpoint lies more than 100 kb upstream of the transcriptional start sites of GJB2 and GJB6. This deletion, del(chr13:19,837,344-19,968,698), segregates as a completely penetrant DFNB1 allele in this family. It is not present in 528 persons with SNHL and monoallelic mutation of GJB2 or GJB6, and we have not identified any other candidate pathogenic copy number variation by arrayCGH in a subset of 10 such persons. Characterization of distant GJB2/GJB6 cis-regulatory regions evidenced by this allele may be required to find the 'missing' DFNB1 mutations that are believed to exist.

Haploinsufficiency of 16.4 Mb from chromosome 22pter-q11.21 in a girl with unilateral conductive hearing loss

We present the postnatal diagnosis of a de novo der(18)t(18;22)(p11.32;q11.21)pat, resulting in an unbalanced 45,XX,der (18)t(18;22) karyotype in a girl with conductive hearing loss on the left and ptosis of the right upper eye-lid. Unilateral ptosis was also observed in the patient's 2 years and 8 months younger sister, who grows noticeably faster and appears to be a much quicker learner. After speech therapy the patient was eventually placed in normal school. The haploinsufficient 16.4-Mb region on chromosome 22pter-->q11.21 contains 10 genes as well as many predicted genes, pseudogenes, and retrotransposed sequences with unknown functions. This observation may prove useful for prenatal diagnosis and genetic counselling of chromosome 22q11.1 gains and losses.

Heavy Ion-induced DNA Double-strand Breaks in Yeast

DNA double-strand break (dsb) induction in diploid yeast was measured by neutral sucrose sedimentation after exposure to very heavy ions with values of linear energy transfer (LET) ranging from about 300 to 11500 ke V/microns. Linear fluence dependencies were found in all cases from which dsb production cross-sections (sigma dsb) could be calculated. Corresponding cross-sections for cell killing (sigma i) were derived from final slopes of survival curves measured in parallel and for the same fluence range. A close correlation was found between sigma i and sigma dsb. It is calculated that over the entire LET range, including 30 MeV electron irradiation, about 22 dsb are induced per lethal event when high exposures are considered.

CADASIL mutations enhance spontaneous multimerization of NOTCH3

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common monogenic cause of stroke and vascular dementia. Disease-causing mutations invariably affect cysteine residues within epidermal growth factor-like repeat domains in the extracellular domain of the NOTCH3 receptor (N3(ECD)). The biochemical and histopathological hallmark of CADASIL is the accumulation of N3(ECD) at the cell surface of vascular smooth muscle cells which degenerate over the course of the disease. The molecular mechanisms leading to N3(ECD) accumulation remain unknown. Here we show that both wild-type and CADASIL-mutated N3(ECD) spontaneously form oligomers and higher order multimers in vitro and that multimerization is mediated by disulfide bonds. Using single-molecule analysis techniques ('scanning for intensely fluorescent targets'), we demonstrate that CADASIL-associated mutations significantly enhance multimerization compared with wild-type. Taken together, our results for the first time provide experimental evidence for N3 self-association and strongly argue for a neomorphic effect of CADASIL mutations in disease pathogenesis.

Humans and chimpanzees differ in their cellular response to DNA damage and non-coding sequence elements of DNA repair-associated genes

Compared to humans, chimpanzees appear to be less susceptible to many types of cancer. Because DNA repair defects lead to accumulation of gene and chromosomal mutations, species differences in DNA repair are one plausible explanation. Here we analyzed the repair kinetics of human and chimpanzee cells after cisplatin treatment and irradiation. Dot blots for the quantification of single-stranded (ss) DNA repair intermediates revealed a biphasic response of human and chimpanzee lymphoblasts to cisplatin-induced damage. The early phase of DNA repair was identical in both species with a peak of ssDNA intermediates at 1 h after DNA damage induction. However, the late phase differed between species. Human cells showed a second peak of ssDNA intermediates at 6 h, chimpanzee cells at 5 h. One of four analyzed DNA repair-associated genes, UBE2A, was differentially expressed in human and chimpanzee cells at 5 h after cisplatin treatment. Immunofluorescent staining of gammaH2AX foci demonstrated equally high numbers of DNA strand breaks in human and chimpanzee cells at 30 min after irradiation and equally low numbers at 2 h. However, at 1 h chimpanzee cells had significantly less DNA breaks than human cells. Comparative sequence analyses of approximately 100 DNA repair-associated genes in human and chimpanzee revealed 13% and 32% genes, respectively, with evidence for an accelerated evolution in promoter regions and introns. This is strikingly contrasting to the 3% of DNA repair-associated genes with positive selection in the coding sequence. Compared to the rhesus macaque as an outgroup, chimpanzees have a higher accelerated evolution in non-coding sequences than humans. The TRF1-interacting, ankyrin-related ADP-ribose polymerase (TNKS) gene showed an accelerated intraspecific evolution among humans. Our results are consistent with the view that chimpanzee cells repair different types of DNA damage faster than human cells, whereas the overall repair capacity is similar in both species. Genetic differences in non-coding sequence elements may affect gene regulation in the DNA repair network and thus contribute to species differences in DNA repair and cancer susceptibility.