A family of mammalian anion transporters and their involvement in human genetic diseases.

Tremendous advances in human genetics have been made in recent years, as the fruits of the Human Genome Project are facilitating the identification of genes associated with myriad genetic diseases. Among the many triumphs in positional (and positional candidate) cloning are a number of cases where apparently unrelated diseases have been found to share common genetic origins. A vivid example of this has unfolded in the past few years with the identification of the genes causing diastrophic dysplasia, congenital chloride diarrhoea and Pendred syndrome. While these three disorders are clinically distinct, the associated genes ( DTDST, CLD and PDS, respectively) emanate from a well conserved family of genes that all encode anion transporters. Our current knowledge of these diseases coupled with new insights about the implicated genes and proteins illustrates the complex nature of mammalian genomes, especially with respect to the evolutionary subtleties of protein families and tissue-specific gene expression.     

CNVs cause autosomal recessive genetic diseases with or without involvement of SNV/indels

PurposeImproved resolution of molecular diagnostic technologies enabled detection of smaller sized exonic level copy-number variants (CNVs). The contribution of CNVs to autosomal recessive (AR) conditions may be better recognized using a large clinical cohort.MethodsWe retrospectively investigated the CNVs’ contribution to AR conditions in cases subjected to chromosomal microarray analysis (CMA, N = ~70,000) and/or clinical exome sequencing (ES, N = ~12,000) at Baylor Genetics; most had pediatric onset neurodevelopmental disorders.ResultsCNVs contributed to biallelic variations in 87 cases, including 81 singletons and three affected sibling pairs. Seventy cases had CNVs affecting both alleles, and 17 had a CNV and a single-nucleotide variant (SNV)/indel in trans. In total, 94.3% of AR-CNVs affected one gene; among these 41.4% were single-exon and 35.0% were multiexon partial-gene events. Sixty-nine percent of homozygous AR-CNVs were embedded in homozygous genomic intervals. Five cases had large deletions unmasking an SNV/indel on the intact allele for a recessive condition, resulting in multiple molecular diagnoses.ConclusionsAR-CNVs are often smaller in size, transmitted through generations, and underrecognized due to limitations in clinical CNV detection methods. Our findings from a large clinical cohort emphasized integrated CNV and SNV/indel analyses for precise clinical and molecular diagnosis especially in the context of genomic disorders.     

Cardiac involvement in systemic autoimmune diseases

The heart and the vascular system are frequent and characteristic targets of several systemic autoimmune diseases, in particular Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA) and Systemic Sclerosis (SSc). In this chapter we review the classic cardiac abnormalities and the more recent data about cardiovascular involvement as part of a major disease complication determining a substantial morbidity and mortality. In addition to the classic cardiac abnormalities involving the heart structures, acute and chronic ischemic heart disease and cerebrovascular accidents are threatening clinical manifestations of SLE and RA associated to an early accelerated atherosclerosis. Immune-mediated inflammation is now recognized as an important factor involved in the pathogenesis of atherosclerosis. Ongoing clinical studies are being devised to find specific risk factors associated with systemic autoimmune diseases and/or treatment regimens. Hopefully, prophylactic measures should be available within the next few years.     

White matter involvement in mitochondrial diseases

White matter involvement is recently being realized as a common finding in mitochondrial disorders. It is considered an inherent part of the classical mitochondrial syndromes which are usually associated with alterations in the mitochondrial DNA such as: Leigh disease, Kearns-Sayre syndrome, mitochondrial encephalomyopathy lactic acidosis, and stroke like episodes, mitochondrial neuro-gastro-intestinal encephalomyopathy and Leber's hereditary optic neuropathy. White matter involvement is also described in mitochondrial disorders due to mutations in the nuclear DNA which are transmitted in an autosomal pattern. MRI findings suggestive of a mitochondrial disease are: small cyst-like lesions in abnormal white matter, involvement of both cerebral and cerebellar white matter, and a combination of a leukoencephalopathy with bilateral basal ganglia lesions. The clinical manifestations may be disproportionate to the extent of white matter involvement. Other organs may frequently be involved. The onset is often in infancy with a neurodegenerative course. The finding of a leukoencephalopathy in a patient with a complex neurologic picture and multisystem involvement should prompt a thorough mitochondrial evaluation.     

Cardiovascular involvement in systemic autoimmune diseases

Autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), primary antiphospholipid syndrome (APS), systemic sclerosis and systemic vasculitis, affect a large number of people in whom one of the leading causes of morbidity and mortality is cardiovascular disease. Cardiovascular disease is associated with the development of accelerated atherosclerosis. It seems to occur at a younger age than in the general population, is often asymptomatic and, in addition to traditional risk factors, also involves specific risk factors as chronic inflammation, the duration and activity of the autoimmune disease, and immunosuppressive therapy. The early phases of cardiovascular involvement in patients with autoimmune diseases may be clinically silent, with only a microcirculation disorder present. There are various means of detecting morphological cardiac damage: coronary angiography remains the gold standard for diagnosing coronary stenosis, but new, non invasive and more reliable methods have been introduced into clinical practice in order to detect subclinical microcirculation abnormalities.     

Collagen diseases with pulmonary involvement]

Pulmonary involvement is a common feature in patients with various collagen diseases. Some types of the pulmonary involvement are resistant to currently available treatment regimens and thus considered as intractable conditions. These include acute/subacute interstitial pneumonia in dermatomyositis, pulmonary interstitial fibrosis in scleroderma, and diffuse alveolar hemorrhage. Acute/subacute interstitial pneumonia with the histology of diffuse alveolar damage (DAD) is mainly occurred in patients with amyopathic or hypomyopathic dermatomyositis who lack autoantibodies to aminoacyl tRNA synthetases. Intensive immunosuppressive treatment in the early phase of the disease may be effective for this intractable complication. Nearly one-third of patients with scleroderma have slowly progressive pulmonary interstitial fibrosis, leading to end-stage respiratory failure. Non-specific interstitial pneumonia (NSIP) with an excessive fibrotic change is a major histology of these patients. There are accumulating evidences showing the effectiveness of cyclophosphamide in patients with this intractable condition, especially those with active alveolitis. Diffuse alveolar hemorrhage is a fatal complication mainly occurred in patients with systemic lupus erythematosus and those with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, including microscopic polyangitis (MPA) and Wegener's granulomatosus. Immediate diagnosis and introduction of intensive treatment are necessary to save the patients with this complication.     

Mosaic mutations in early-onset genetic diseases

PurposeAn emerging approach in medical genetics is to identify de novo mutations in patients with severe early-onset genetic disease that are absent in population controls and in the patient’s parents. This approach, however, frequently misses post-zygotic “mosaic” mutations that are present in only a portion of the healthy parents’ cells and are transmitted to offspring.MethodsWe constructed a mosaic transmission screen for variants that have an ~50% alternative allele ratio in the proband but are significantly less than 50% in the transmitting parent. We applied it to two family-based genetic disease cohorts consisting of 9 cases of sudden unexplained death in childhood (SUDC) and 338 previously published cases of epileptic encephalopathy.ResultsThe screen identified six parental-mosaic transmissions across the two cohorts. The resultant rate of ~0.02 identified transmissions per trio is far lower than that of de novo mutations. Among these transmissions were two likely disease-causing mutations: an SCN1A mutation transmitted to an SUDC proband and her sibling with Dravet syndrome, as well as an SLC6A1 mutation in a proband with epileptic encephalopathy.ConclusionThese results highlight explicit screening for mosaic mutations as an important complement to the established approach of screening for de novo mutations.     

多聚丙氨酸延展突变与人类遗传病

三核苷酸重复的延展突变是导致遗传病的重要机制之一。根据产生机制和遗传特点的不同,可将其分为2类：一类是引起多种神经系统遗传病的动态突变;另一类就是本文重点介绍的多聚丙氨酸延展（polyalanine expansion,PAE）突变。PAE是指编码多聚丙氨酸的不完全GCN（N为A、C、G或T中任意一种）三核苷酸重复的延展,其结果是蛋白中多聚丙氨酸链的氨基酸数增多。PAE突变能在世代间稳定传递,其产生机制可能为等位基因间的不等交换。迄今为止,已在9种遗传病中发现PAE突变。本文将对PAE突变及所致遗传病作一介绍。     

Central nervous system involvement in connective tissue diseases]

Neuropsychiatric manifestations are relatively common and serious complications in systemic lupus erythematosus (CNS lupus). Overall, in patients with CNS lupus, CSF IgM, IgA, IgG indexes (indicators of intrathecal Ig synthesis) as well as CSF IL-6 activities were significantly elevated. Of note, especially in patients lupus psychosis, but not in those with focal CNS lesions, anti-ribosomal P antibody (anti-P) in the sera as well as anti-neuronal antibody (anti-N) in the CSF was significantly elevated in relation to their CNS disease activities. These data indicate that the immune system activation within the CNS, possibly resulting in the elevation of CSF anti-N, plays an important role in the pathogenesis of CNS lupus, including lupus psychosis. CNS involvement in Beh?et's disease, usually called neuro-Beh?et's syndrome (NB), includes acute type and chronic progressive type. Acute NB is characterized by acute meningoencephalitis with focal lesions, presenting high intensity areas in T2-weightened images or Flare images on MRI scans, whereas chronic progressive NB is characterized by intractable slowly progressive dementia, ataxia and dysarthria with persistent elevation of CSF IL-6 activity. Chronic progressive NB is resistant to conventional treatment with steroid, cyclophosphamide, or azathioprine, but responds to low dose methotrexate. As for ANCA-related vasculitis, pachymeningitis has been found to be associated with P-ANCA as well as C-ANCA.     

Regulation of iron metabolism and its involvement in diseases

Iron is an essential nutrient virtually almost all organisms including human, but at the same time, it is toxic because its high reactivity to molecular oxygen generates free radicals. Therefore, iron metabolism is tightly regulated. Recently, knowledge of roles that iron plays in our body as well as regulatory mechanism of iron metabolism in human body has been drastically expanded. Here I describe recent advance in our understanding on the regulation of iron metabolism and discuss its relationship to various diseases.     

Vitamin D endocrine system involvement in autoimmune rheumatic diseases

Vitamin D is synthesized from cholesterol in the skin (80-90%) under the sunlight and then metabolized into an active D hormone in liver, kidney and peripheral immune/inflammatory cells. These endocrine-immune effects include also the coordinated activities of the vitamin D-activating enzyme, 1alpha-hydroxylase (CYP27B1), and the vitamin D receptor (VDR) on cells of the immune system in mediating intracrine and paracrine actions. Vitamin D is implicated in prevention and protection from chronic infections (i.e. tubercolosis), cancer (i.e. breast cancer) and autoimmune rheumatic diseases since regulates both innate and adaptive immunity potentiating the innate response (monocytes/macrophages with antimicrobial activity and antigen presentation), but suppressing the adaptive immunity (T and B lymphocyte functions). Vitamin D has modulatory effects on B lymphocytes and Ig production and recent reports have demonstrated that 1,25(OH)2D3 does indeed exert direct effects on B cell homeostasis. A circannual rhythm of trough vitamin D levels in winter and peaks in summer time showed negative correlation with clinical status at least in rheumatoid arthritis and systemic lupus erythematosus. Recently, the onset of symptoms of early arthritis during winter or spring have been associated with greater radiographic evidence of disease progression at 12 months possibly are also related to seasonal lower vitamin D serum levels.     

Preimplantation diagnosis of genetic diseases

One of the landmarks in clinical genetics is prenatal diagnosis of genetic disorders. The recent advances in the field have made it possible to diagnose the genetic conditions in the embryos before implantation in a setting of in vitro fertilization. Polymerase chain reaction and fluorescence in situ hybridization are the two common techniques employed on a single or two cells obtained via embryo biopsy. The couple who seek in vitro fertilization may screen their embryos for aneuploidy and the couple at risk for a monogenic disorder but averse to abortion of the affected fetuses after prenatal diagnosis, are likely to be the best candidates to undergo this procedure. This article reviews the technique, indications, benefits, and limitations of pre-implantation genetic testing in clinical practice.     

Protein misfolding and degradation in genetic diseases

Investigations of genetic diseases such as cystic fibrosis, α‐1‐antitrypsin deficiency, phenylketonuria, mitochondrial acyl‐CoA dehydrogenase deficiencies, and many others have shown that enhanced proteolytic degradation of mutant proteins is a common molecular pathological mechanism. Detailed studies of the fate of mutant proteins in some of these diseases have revealed that impaired or aberrant folding of mutant polypeptides typically results in prolonged interaction with molecular chaperones and degradation by intracellular proteases before the functional conformation is acquired. This appears to be the case for many missense mutations and short in‐frame deletions or insertions that represent a major fraction of the mutations detected in genetic diseases. In some diseases, or under some circumstances, the degradation system is not efficient. Instead, aberrant folding leads to accumulation of protein aggregates that damage the cell. Mechanisms by which misfolded proteins are selected for degradation have first been delineated for the endoplasmatic reticulum; this process has been termed "protein quality control." Similar mechanisms appear to be operative in all cellular compartments in which proteins fold. Within the context of genetic diseases, we review knowledge on the molecular processes underlying protein quality control in the various subcellular compartments. The important impact of such systems for variability of the expression of genetic deficiencies is emphasised. Hum Mutat 14:186–198, 1999. © 1999 Wiley‐Liss, Inc.     

Cis- and trans- mutations in genetic diseases

Whereas a great number of mutations located in the coding regions of genes have been described, genetic defects involving regulatory elements (cis-) or diffusible effectors controlling gene expression (trans-) are poorly known. Moreover, it appears that the structural defects of transcribed regions of genes have already delivered their "conceptual" message, whereas few studies of the consequences of one single gene defect on the expression of other genes and on in vivo functions are available. In the present communication, we wish to address the following issue: can we take advantage of Nature's experiments, ie. diseases, to extend our knowledge of the coordinate regulation of gene expression, via an original pathway, ie. the pathophysiological pathway? Can we select a few inborn or acquired metabolic diseases as models which could provide insight into as yet unknown factors involved in trans- regulation of gene expression?     

Immuno- and genetic therapy in autoimmune diseases

Animal models of autoimmune disease have been developed that mimic some aspects of the pathophysiology of human disease. These models have increased our understanding of possible mechanisms of pathogenesis at the molecular and cellular level and have been important in the testing, development and validation of new immunotherapies. The susceptibility to develop disease in the majority of these models is polygenic as is the case in humans. The exceptions to this rule are gene knock outs and transgenic models of particular genes which, in particular genetic backgrounds, have also contributed to the understanding of single gene function and their possible contribution to pathogenesis. Gene therapy approaches that target immune functions are being developed with encouraging results, despite the polygenic nature of these diseases. Basically this novel immuno-genetic therapy harnesses the knowledge of immunology with the myriad of biotechnological breakthroughs in vector design and delivery. Autoimmune disease is the result of genetic dysregulation which could be controlled by gene therapy. Here we summarize the genetic basis of these human diseases as well as some of the best characterized murine models. We discuss the strategies for their treatment using immuno- and gene therapy.     

Arterial supply to the tibial tuberosity: involvement in patellar ligament transfer in children

Purpose  

The aims were to study arterial blood supply of the tibial tuberosity, and to evaluate its remaining blood supply after patellar ligament transposition in children.