FOXP3调控中的表观遗传学现象

FOXP3转录因子是维持调节性T细胞(Treg)免疫抑制功能的必要条件。研究发现FOXP3也可在抗原受体激活的非调节性T细胞表达,使其作为Treg的特异性标志受到质疑。实验证明Treg细胞的FOXP3基因座含有多个去甲基化区域,且似乎更有特异性。FOXP3基因表达和蛋白功能发挥随着组蛋白甲基化和乙酰化水平而改变。DNA甲基化转移酶抑制剂(DNMTi)或组蛋白去乙酰化酶抑制剂(HDACi)可诱导具有免疫抑制功能的Treg产生。本文对FOXP3基因表达调控,蛋白修饰后调节其它基因表达过程中的表观遗传学现象及临床应用前景作一综述。     

Anderson's disease (chylomicron retention disease): a new mutation in the SARA2 gene associated with muscular and cardiac abnormalities

Anderson's disease (AD) or chylomicron retention disease (CMRD) is a rare hereditary lipid malabsorption syndrome linked to SARA2 gene mutations. We report in this study a novel mutation in two sisters for which the Sar1b protein is predicted to be truncated by 32 amino acids at its carboxyl-terminus. Because the SARA2 gene is also expressed in the muscle, heart, liver and placenta, extraintestinal clinical manifestations may exist. For the first time, we describe in this study in the two sisters muscular as well as cardiac abnormalities that could be related to the reported expression of SARA2 in these tissues. We also evaluated six other patients for potential manifestations of the SARA2 mutation. The creatine phosphokinase levels were increased in all patients [1.5-9.4 x normal (N)] and transaminases were moderately elevated in five of the eight patients (1.2-2.6 x N), probably related to muscle disease rather than to liver dysfunction. A decreased ejection fraction occurred in one patient (40%, N: 60%). The muscle, liver and placental tissues that were examined had no specific abnormalities and, in particular, no lipid accumulation. These results suggest that myolysis and other extraintestinal abnormalities can occur in AD/CMRD and that the clinical evaluation of patients should reflect this.     

PTPN11 gene mutation associated with abnormal gonadal determination

Germline mutations in the PTPN11 gene have been associated with Noonan syndrome (NS) and LEOPARD syndrome. Both germline and somatic mutations in this gene have been reported in association with malignancies. However, the T507K mutation in the PTPN11 gene, has only been reported in malignancies and in a fetus with hydrops fetalis but not in a live patient with NS. We report the autopsy findings in a fetus with the T507K mutation who presented prenatally with hydrops fetalis, cystic hygroma and 46, XX karyotype. On autopsy, the patient was found to have testes, male external genitalia, but absent Wolffian ducts.     

A missense mutation in the OCTN2 gene associated with residual carnitine transport activity

Primary carnitine deficiency is an autosomal recessive disorder of fatty acid oxidation caused by defective carnitine transport. This disease can present early in life with hypoketotic hypoglycemia and acute metabolic decompensation, or later in life with skeletal or cardiac myopathy. Mutations abolishing the function of OCTN2, an organic cation/carnitine transporter with twelve putative transmembrane spanning domains, were recently demonstrated in patients with early- and late-onset (up to seven years of age) presentation of this syndrome. Most of the reported mutations are null alleles. Here we evaluate the OCTN2 gene in a male patient who presented at seven years of age with severe dilated cardiomyopathy. Plasma carnitine levels were undetectable and carnitine transport by his fibroblasts was reduced to about 3% of normal controls. This patient was homozygous for a single base pair change in exon 8 of the OCTN2 gene (1354G>A) converting the codon for Glu 452 to Lys (E452K) in the predicted intracellular loop between transmembrane domains 10 and 11. Stable expression of the mutant E452K-OCTN2 cDNA in Chinese hamster ovary (CHO) cells caused a partial increase in carnitine transport to 2-4% of the levels measured in the wild type transporter. This reduced transport activity was associated with normal Km toward carnitine (3.1 +/- 1.1 microM), but markedly reduced Vmax. These results indicate that primary carnitine deficiency can be caused by mutations encoding for carnitine transporters with residual activity, and that the E452K affects a domain not involved in carnitine recognition.     

Evaluation of FOXP2 as an autism susceptibility gene

A mutation in the gene FOXP2 was recently identified as being responsible for a complicated speech and language phenotype in a single large extended pedigree. This gene is of interest to autism because it lies in one of the most consistently linked autism chromosomal regions of interest. We therefore tested this gene for its involvement in autism in a large sample of autism families. We completely sequenced the exon containing the mutation, screened the remaining coding sequence using SSCP technology, and identified and genotyped two novel intronic tetranucleotide repeat polymorphisms that were then analyzed for evidence of linkage and linkage disequilibrium (LD). We identified two families in which heterozygous deletions of a small number of glutamines in a long poly-glutamine stretch were found in one parent and the autistic probands; no other non-conservative coding sequence changes were identified. Linkage and LD analyses were performed in 75 affected sibling pair families and in two subgroups of this sample defined by the presence/absence of severe language impairment. One allele appeared to have an opposite pattern of transmission in the language based subgroups, but otherwise the linkage and LD analyses were negative. We conclude that FOXP2 is unlikely to contribute significantly to autism susceptibility.     

DNAH2 is a novel candidate gene associated with multiple morphological abnormalities of the sperm flagella

Multiple morphological abnormalities of flagella (MMAF) is one kind of severe teratozoospermia. Gene mutations reported in previous works only revealed the pathogenesis of approximately half of the MMAF cases, and more genetic defects in MMAF need to be explored. In the present study, we performed a genetic analysis on Han Chinese men with MMAF using whole-exome sequencing. After filtering out the cases with known gene mutations, we identified five novel mutation sites in the DNAH2 gene in three cases from three families. These mutations were validated through Sanger sequencing and absent in all control individuals. In silico analysis revealed that these DNAH2 variations are deleterious. The spermatozoa with DNAH2 mutations showed severely disarranged axonemal structures with mitochondrial sheath defection. The DNAH2 protein level was significantly decreased and inner dynein arms were absent in the spermatozoa of patients. ICSI treatment was performed for two MMAF patients with DNAH2 mutations and the associated couples successfully achieved pregnancy, indicating good nuclear quality of the sperm from the DNAH2 mutant patients. Together, these data suggest that the DNAH2 mutation can cause severe sperm flagella defects that damage sperm motility. These results provide a novel genetic pathogeny for the human MMAF phenotype.     

Dysbindin gene variability is associated with cognitive abnormalities in first-episode non-affective psychosis

Introduction. Dystrobrevin-binding protein 1 gene (dysbindin or DTNBP1) has been associated with schizophrenia and cognitive performance. Its expression in areas implicated in cognition such as the dorsolateral prefrontal cortex, as well as its role in dopaminergic and glutamatergic system, has been replicated by several studies. The main aim of this study was to examine the association between DTNBP1 variability and cognitive performance in a sample of 238 patients with a first episode of a non-affective psychosis.

Methods. Patients, and a comparison sample of 47 healthy subjects, completed an extensive neuropsychological battery. Five single nucleotide polymorphisms (SNPs) within DTNBP1 (rs2619528, rs2619538, rs3213207, rs2619539 and rs760761) and three haplotypes (GACAC, GAGAC and GTGAC) were analysed.

Results. In the group of patients, we found a significant association between two of the DTNBP1 SNPs and one of the haplotypes (rs2619539, rs3213207 and GACAC) and a measure of premorbid IQ [Wechsler Adult Intelligence Scale-3rd Edition (WAIS-III) Vocabulary subtest]. Moreover, one of these SNPs, rs2619539, was also associated with our measure of working memory (WAIS-III Backward digits subtest) and two haplotypes, GAGAC and GTGAC, with our measure of verbal memory (Rey Auditory Verbal Learning Test), of visual memory (Rey Complex Figure Test) in the case of GAGAC, and of speed of processing (WAIS-III Digit Symbol-coding) in the case of GTGAC.

Conclusions. Our findings add further evidence suggesting an association between dysbindin gene variability and cognitive abnormalities in schizophrenia, providing preliminary evidence of this association since the time of illness onset among minimally medicated patients.     

A nonsense mutation in the LIMP-2 gene associated with progressive myoclonic epilepsy and nephrotic syndrome

The main clinical features of two siblings from a consanguineous marriage were progressive myoclonic epilepsy without intellectual impairment and a nephrotic syndrome with a strong accumulation of C1q in capillary loops and mesangium of kidney. The biochemical analysis of one of the patients revealed a normal beta-glucocerebrosidase activity in leukocytes, but a severe enzymatic deficiency in cultured skin fibroblasts. This deficiency suggested a defect in the intracellular sorting pathway of this enzyme. The sequence analysis of the gene encoding LIMP-2 (SCARB2), the sorting receptor for beta-glucocerebrosidase, confirmed this hypothesis. A homozygous nonsense mutation in codon 178 of SCARB2 was found in the patient, whereas her healthy parents were heterozygous for the mutation. Besides lacking immunodetectable LIMP-2, patient fibroblasts also had decreased amounts of beta-glucocerebrosidase, which was mainly located in the endoplasmic reticulum, as assessed by its sensitivity to Endo H. This is the first report of a mutation in the SCARB2 gene associated with a human disease, which, contrary to earlier proposals, shares no features with Charcot-Marie-Tooth disease both at the clinical and neurophysiological levels.     

Loss-of-function mutation in DNAH8 induces asthenoteratospermia associated with multiple morphological abnormalities of the sperm flagella

Asthenozoospermia is a common cause of male infertility associated with the reduced motility and/or abnormal morphology of spermatozoa, although its etiology remains incompletely understood. Multiple morphological abnormalities of the sperm flagella (MMAF) is one of the main causes of asthenozoospermia. However, the MMAF-associated genes identified to date cannot explain all the human MMAF cases. Herein, a loss-of-function mutation of DNAH8 was identified in an asthenozoospermia patient with MMAF. Moreover, the negative effect of this mutation on DNAH8 expression was confirmed by immunofluorescence staining and western blotting. Remarkably, it is the first time that DNAH8 is suggested to be associated with human MMAF. Our findings provide strong evidence that a loss-of-function mutation in DNAH8 can cause male infertility with MMAF and that DNAH8 is essential for sperm flagellar formation.