The major function of vascular smooth muscle cells (SMCs) is contraction to regulate blood pressure and flow. SMC contractile force requires cyclic interactions between SMC alpha-actin (encoded by ACTA2) and the beta-myosin heavy chain (encoded by MYH11). Here we show that missense mutations in ACTA2 are responsible for 14% of inherited ascending thoracic aortic aneurysms and dissections (TAAD). Structural analyses and immunofluorescence of actin filaments in SMCs derived from individuals heterozygous for ACTA2 mutations illustrate that these mutations interfere with actin filament assembly and are predicted to decrease SMC contraction. Aortic tissues from affected individuals showed aortic medial degeneration, focal areas of medial SMC hyperplasia and disarray, and stenotic arteries in the vasa vasorum due to medial SMC proliferation. These data, along with the previously reported MYH11 mutations causing familial TAAD, indicate the importance of SMC contraction in maintaining the structural integrity of the ascending aorta.

Permanent neonatal diabetes (PND) can be caused by mutations in the transcription factors insulin promoter factor (IPF)-1, eukaryotic translation initiation factor-2␣ kinase 3 (EIF2AK3), and forkhead box-P3 and in key components of insulin secretion: glucokinase (GCK) and the ATP-sensitive K؉ channel subunit Kir6.2. We sequenced the gene encoding Kir6.2 (KCNJ11) in 11 probands with GCK-negative PND. Heterozygous mutations were identified in seven probands, causing three novel (F35V, Y330C, and F333I) and two known (V59M and R201H) Kir6.2 amino acid substitutions. Only two probands had a family history of diabetes. Subjects with the V59M mutation had neurological features including motor delay. Three mutation carriers tested had an insulin secretory response to tolbutamide, but not to glucose or glucagon. Glibenclamide was introduced in increasing doses to investigate whether sulfonylurea could replace insulin. At a glibenclamide dose of 0.3-0.4 mg ⅐ kg ؊1 ⅐ day ؊1 , insulin was discontinued. Blood glucose did not deteriorate, and HbA 1c was stable or fell during 2-6 months of follow-up. An oral glucose tolerance test performed in one subject revealed that glucose-stimulated insulin release was restored. Mutations in Kir6.2 were the most frequent cause of PND in our cohort. Apparently insulin-dependent patients with mutations in Kir6.2 may be managed on an oral sulfonylurea with sustained metabolic control rather than insulin injections, illustrating the principle of pharmacogenetics applied in diabetes treatment. Diabetes 53: [2713][2714][2715][2716][2717][2718] 2004 N eonatal diabetes may be defined as hyperglycemia diagnosed within the first 3 months of life (1). Transient neonatal diabetes is associated with abnormalities in chromosome 6 (2), whereas the permanent form may be caused by mutations in the genes encoding the transcription factors insulin promoter factor (IPF)-1 (3,4), eukaryotic translation initiation factor-2␣ kinase 3 (EIF2AK3) (5), forkhead box-P3 (6), and the glucose-sensing enzyme glucokinase (GCK) (7,8). Gloyn et al. (9) recently identified that the ATPsensitive K ϩ channel subunit Kir6.2 can cause PND. We here report nine new cases of PND associated with mutations in the gene KCNJ11 encoding Kir6.2. In addition, we also show that oral therapy with a sulfonylurea drug should be considered in patients with mutations in Kir6.2. RESEARCH DESIGN AND METHODSThe neither systematic nor population-based screening included 16 referred probands with PND from Norway, Israel, Italy, Turkey, and the U.S. (8,10). Informed consent was obtained from the subjects or their parents. The studies were performed according to the Declaration of Helsinki and approved by ethics committees. Genetic studies. KCNJ11 encoding Kir6.2 was sequenced as previously described (9). Microsatellite markers localized to four different chromosomes were used to confirm family relationships. Clinical studies. A common protocol was carried out for all participating centers. The medical records of mutation carriers were reviewed ...

Although many of the phenotypic features of our patients are rather nonspecific in cohorts of individuals with syndromic and nonsyndromic mental retardation, the proneness to infection is quite striking because the patients had normal growth and were not physically debilitated. Although the etiology of the infections is not understood, we recommend considering MECP2 dosage studies and a genetics referral in individuals with severe developmental delay and neurologic findings, especially when a history of recurrent respiratory ailments has been documented.

Autosomal recessive cutis laxa type 2 (ARCL2), a syndrome of growth and developmental delay and redundant, inelastic skin, is caused by mutations in the a2 subunit of the vesicular ATPase H+-pump (ATP6V0A2). The goal of this study was to define the disease mechanisms that lead to connective tissue lesions in ARCL2. In a new cohort of 17 patients, DNA sequencing of ATP6V0A2 detected either homozygous or compound heterozygous mutations. Considerable allelic and phenotypic heterogeneity was observed, with a missense mutation of a moderately conserved residue p.P87L leading to unusually mild disease. Abnormal N- and/or mucin type O-glycosylation was observed in all patients tested. Premature stop codon mutations led to decreased ATP6V0A2 mRNA levels by destabilizing the mutant mRNA via the nonsense-mediated decay pathway. Loss of ATP6V0A2 either by siRNA knockdown or in ARCL2 cells resulted in distended Golgi cisternae, accumulation of abnormal lysosomes and multivesicular bodies. Immunostaining of ARCL2 cells showed the accumulation of tropoelastin (TE) in the Golgi and in large, abnormal intracellular and extracellular aggregates. Pulse-chase studies confirmed impaired secretion and increased intracellular retention of TE, and insoluble elastin assays showed significantly reduced extracellular deposition of mature elastin. Fibrillin-1 microfibril assembly and secreted lysyl oxidase activity were normal in ARCL2 cells. TUNEL staining demonstrated increased rates of apoptosis in ARCL2 cell cultures. We conclude that loss-of-function mutations in ATP6V0A2 lead to TE aggregation in the Golgi, impaired clearance of TE aggregates and increased apoptosis of elastogenic cells.