TET2 Mutation and High miR-22 Expression as Biomarkers to Predict Clinical Outcome in Myelodysplastic Syndrome Patients Treated with Hypomethylating Therapy

Tet methylcytosine dioxygenase 2 (TET2) is one of the most frequently mutated genes in myelodysplastic syndrome (MDS). TET2 is known to involve a demethylation process, and the loss of TET2 is thought to cause DNA hypermethylation. Loss of TET2 function is known to be caused by genetic mutations and miRNA, such as miR-22. We analyzed 41 MDS patients receiving hypomethylating therapy (HMT) to assess whether TET2 mutation status and miR-22 expression status were associated with their clinical characteristics and treatment outcomes. Responsiveness to HMT was not affected by both TET2 mutation (odds ratio (OR) 0.900, p = 0.909) and high miR-22 expression (OR 1.548, p = 0.631). There was a tendency for TET2 mutation to be associated with lower-risk disease based on IPSS (Gamma = −0.674, p = 0.073), lower leukemic transformation (OR 0.170, p = 0.040) and longer survival (Hazard ratio 0.354, p = 0.059). Although high miR-22 expression also showed a similar tendency, this tendency was weaker than that of TET2 mutation. In summary, the loss of TET2 function, including both TET2 mutation and high miR-22 expression, was not a good biomarker for predicting the response to HMT but may be associated with lower-risk disease based on IPSS, lower leukemic transformation and longer survival.     

老年痴呆的遗传机制研究进展

老年痴呆症,又称阿尔茨海默病(Alzheimer’s disease,AD),是威胁老年人健康的主要疾病之一。根据发病年龄,AD可分为早发性(early-onset Alzheimer’s disease,EOAD)和迟发性(late-onset Alzheimer’s disease,LOAD)两种,两者均受到遗传因素的影响。目前已知3个致病基因导致家族性EOAD的发病:淀粉样前体蛋白基因(β-amyloid precursor protein,APP)、早老素1基因(presenilin 1,PSEN1)和早老素2基因(presenilin 2,PSEN2)。而近年来在全基因组关联分析(genome-wide association study,GWAS)等新技术的支持下,研究者相继发现并报道了一系列影响LOAD易感性的风险基因多态性位点。试对上述AD相关致病基因和主要风险基因加以简要介绍,深入探索这些基因的功能有助于对AD病理生理机制的认知。     

Functional effects of mutations identified in patients with multiminicore disease

Multiminicore disease is a recessive congenital myopathy characterized by the presence of small cores or areas lacking oxidative enzymes, in skeletal muscle fibres. From a clinical point of view, the condition is widely heterogeneous and at least four phenotypes have been identified; genetic analysis has revealed that most patients with the classical form of multiminicore characterized by rigidity of the spine, early onset and respiratory impairment harbour recessive mutations in the SEPN1 gene, whereas the majority of patients belonging to the other categories, including patients with ophthalmoplegia or patients with a phenotype similar to central core disease, carry recessive mutations in the RYR1. In the present review we discuss the most recent findings on the functional effect of mutations in SEPN1 and RYR1 and discuss how they may adversely affect muscle function and lead to the clinical phenotype.     

Overexpression of miR-125a in Myelodysplastic Syndrome CD34+ Cells Modulates NF-κB Activation and Enhances Erythroid Differentiation Arrest

Myelodysplastic syndromes (MDS) are characterized by impaired proliferation and differentiation of hematopoietic stem cells. The participation of toll-like receptor (TLR)-mediated signaling in MDS is well documented. Increased TLR signaling leads to the constitutive activation of NF-κB, which mediates inflammation, cell proliferation and apoptosis. In addition, the TLR pathway induces the expression of miRNAs which participate in the fine-tuning of the inflammatory response. miRNAs also regulate other biological processes, including hematopoiesis. miR-125a and miR-125b are known modulators of hematopoiesis and are abnormally expressed in several hematologic malignancies. However, little is known about their role in MDS. NF-κB-activating ability has been described for both miRNAs. We studied the role of miR-125a/miR-125b in MDS and their relationship with TLR signaling and hematopoietic differentiation. Our results indicate that miR-125a is significantly overexpressed in MDS patients and correlates negatively with patient survival. Expression of miR-99b, which is clustered with miR-125a, is also directly correlated with prognosis of MDS. Both miR-125a and miR-99b activated NF-κB in vitro; however, we observed a negative correlation between miR-99b expression and the levels of TLR2, TLR7 and two downstream genes, suggesting that NF-κB activation by the miRNA cluster occurs in the absence of TLR signaling. We also show that TLR7 is negatively correlated with patient survival in MDS. In addition, our data suggest that miR-125a may act as an NF-κB inhibitor upon TLR stimulation. These results indicate that miR-125a is involved in the fine-tuning of NF-κB activity and that its effects may depend on the status of the TLR pathway. Furthermore, we observed that miR-125a inhibits erythroid differentiation in leukemia and MDS cell lines. Therefore, this miRNA could serve as a prognostic marker and a potential therapeutic target in MDS.     

Retinitis pigmentosa: genes and disease mechanisms

Retinitis pigmentosa (RP) is a group of inherited disorders affecting 1 in 3000-7000 people and characterized by abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium of the retina which lead to progressive visual loss. RP can be inherited in an autosomal dominant, autosomal recessive or X-linked manner. While usually limited to the eye, RP may also occur as part of a syndrome as in the Usher syndrome and Bardet-Biedl syndrome. Over 40 genes have been associated with RP so far, with the majority of them expressed in either the photoreceptors or the retinal pigment epithelium. The tremendous heterogeneity of the disease makes the genetics of RP complicated, thus rendering genotype-phenotype correlations not fully applicable yet. In addition to the multiplicity of mutations, in fact, different mutations in the same gene may cause different diseases. We will here review which genes are involved in the genesis of RP and how mutations can lead to retinal degeneration. In the future, a more thorough analysis of genetic and clinical data together with a better understanding of the genotype-phenotype correlation might allow to reveal important information with respect to the likelihood of disease development and choices of therapy.     

LRRK2 mutations and neurotoxicant susceptibility

Interactions between genetic and environmental factors are thought to contribute to the pathogenesis of the majority of Parkinson’s disease (PD) cases. However, our understanding of these interactions is at an early stage. Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of hereditary PD. Penetrance of LRRK2 mutations is incomplete and variable, suggesting that other environmental or genetic factors may contribute to the development of the disorder. Recently, using animal models, several attempts have been made to understand if LRRK2 may mediate sensitivity to environmental neurotoxicants. Here, we critically review the most current data on how LRRK2 mutations influence neurotoxicity in PD models.     

Molecular pathways mediating MDS/AML with focus on AML1/RUNX1 point mutations

AML1/RUNX1 point mutations have been identified in myelodysplastic syndrome (MDS) and MDS‐related acute myeloid leukemia (AML), or MDS/AML, and are distributed throughout the full length of AML1/RUNX1. Gene mutation is proposed to be one of the disease‐defining genetic abnormalities of MDS/AML. Most of the mutants lose trans‐activation potential, which leads to a loss of normal function indicating that AML1/RUNX1 dysfunction is one of the major pathogenic mechanisms of MDS/AML. However, N‐terminal in‐frame mutations (Ni‐type) and C‐terminal truncated mutations (Ct‐type) of AML1/RUNX1 show a dominant‐negative effect on the trans‐activation activity, suggesting that these types of mutants may have some oncogenic potential in addition to the loss of normal function. The patients with Ni‐type mutations have hypoplastic marrows with other genetic abnormalities, whereas the patients with Ct‐type mutations display hyperplastic marrows without other mutations. Although biological analysis using a mouse bone marrow transplantation model transduced with Ni‐type of D171N or Ct‐type of S291fsX300 mutants has partially confirmed the oncogenic ability of AML1 mutants, it could not explain the mutant specific clinical features of MDS/AML. Biological analysis using human CD34⁺ cells revealed that the two types exhibited distinct molecular mechanisms. Ni‐type shows differentiation block without cell growth, but additional BMI‐1‐expression resulted in increased blastic cells. In contrast, Ct‐type itself has proliferation ability. Thus, AML1/RUNX1 mutants play a central role in the pathogenesis of MDS/AML. Both AML1 mutants are initiating factors for MDS‐genesis by inhibiting differentiation of hematopoietic stem cells, and Ni‐type mutant requires acquisition of proliferation ability. J. Cell. Physiol. 220: 16–20, 2009. © 2009 Wiley‐Liss, Inc.     

How mitochondrial damage affects cell function

The pathophysiology of mitochondrial DNA (mtDNA) diseases is caused by increased cell death and dysfunction due to the accumulation of mutations to mtDNA. While the disruption of oxidative phosphorylation is central to mtDNA diseases, many other factors, such as Ca²⁺ dyshomeostasis, increased oxidative stress and defective turnover of mitochondrial proteins, may also contribute. The relative importance of these processes in causing cell dysfunction and death is uncertain. It is also unclear whether these damaging processes lead to the disease phenotype through affecting cell function, increasing cell death or a combination of both. These uncertainties limit our understanding of mtDNA disease pathophysiology and our ability to develop rational therapies. Here, we outline how the accumulation of mtDNA mutations can lead to cell dysfunction by altering oxidative phosphorylation, Ca²⁺ homeostasis, oxidative stress and protein turnover and discuss how these processes affect cell function and susceptibility to cell death. A better understanding of these processes will eventually clarify why particular mtDNA mutations cause defined syndromes in some cases but not in others and why the same mutation can lead to different phenotypes.     

The wobbler mouse

Various mutations in humans and animals lead to the selective and progressive degeneration of motoneurons, resulting in muscular weakness, subsequent paralysis, and death (1-3). Amyotrophic lateral sclerosis (ALS) is the most common adult human motoneuron disease, but the vast majority of sporadic and familial cases of ALS are still of unknown origin (4). Murine models of motoneuron diseases, derived from spontaneous mutations in the colonies, have been known for half a century. Prior to the first identifications of the mutated proteins in human ALS, they have largely been used to explore the disease etiology. The chromosomal localization of these mutations does not favor a genetic similarity between these murine models and the few human forms of the disease for which the mutation or the chromosomal localization is known. Yet the fact that most human ALS cases are of unknown etiology and the recent discovery of molecules with no known role in motoneuron survival (5-7), indicate that these murine mutants may still contribute to the understanding of motoneuronal degenerative processes. This can be exemplified by the work performed on the wobbler mouse, one of the oldest and most extensively studied models, which is reviewed here.     

Alternate Causes for Pathogenesis of Exfoliation Glaucoma,a Multifactorial Elastotic Disorder: A Literature Review

Exfoliation glaucoma (XFG) is the most recognizable form of secondary open-angle glaucoma associated with a high risk of blindness. This disease is characterized by white flaky granular deposits in the anterior chamber that leads to the elevation of intraocular pressure (IOP) and subsequent glaucomatous optic nerve damage. Conventionally, XFG is known to respond poorly to medical therapy, and surgical intervention is the only management option in most cases. Various genetic and nongenetic factors are known to be linked to the development of XFG. Despite decades of research on the genetic factors in exfoliation syndrome (XFS) by study groups and global consortia involving different ethnic populations, the pathogenesis of XFS and the mechanism of onset of glaucoma still remains an unsolved mystery. The key lies in understanding how the function of a gene (or set of genes) is altered by environmental triggers, along with other molecular events that underlie the key disease attributes, namely, oxidative stress and the disruption of the blood–aqueous barrier (BAB). It remains a challenge to evolve a theory encompassing all factions of molecular events occurring independently or parallelly that determine the disease manifestation (phenotype) or the stage of the disease in the eye (or in any tissue) in exfoliation. Our enhanced understanding of the underlying molecular pathophysiology of XFG, beyond the known genes or polymorphisms involved in the disease, will lead to improved diagnosis and management and the ability to recognize how the environment influences these key events that lead to the disease phenotype or disease progression. This review summarizes the recent observations and discoveries of four key factors that may hold the answers to the non-lysyl oxidase-like 1 (LOXL1) mechanisms behind XFG pathogenesis, namely, the epigenetic factor miRNA, disordered autophagy along with the potential involvement of mitochondrial mutations, and a compromised aqueous–blood barrier.     

青少年GATA2缺陷继发骨髓增生异常综合征一例并文献复习

摘要 目的：提高对青少年GATA2缺陷继发骨髓增生异常综合征（MDS）疾病的认识。方法：回顾性分析我院收治的1例青少年GATA2缺陷继发MDS患者的诊疗过程,并结合相关文献进行复习总结。结果：患者男,17岁,2018年6月于我科诊断为MDS(MDS-EB-I,IPSS中危-1;WPSS高危;IPSS-R高危),继发骨髓纤维化。完善血液遗传全外显子基因检查提示患者GATA2基因突变。修正诊断为GATA2缺陷综合征、继发MDS( MDS-EB-I,IPSS中危-1;WPSS高危;IPSS-R高危) 、继发骨髓纤维化。完善患者姐姐血常规检查提示白细胞轻度减少,检查患者姐姐GATA2基因检测到GATA2基因错义突变。患者治疗期间反复出现多部位感染。进一步检查患者父母GATA2基因提示患者父亲GATA2基因存在错义突变。患者GATA2基因突变系父系遗传。结论：对于青少年MDS患者,应对其进行血液遗传学全外显子基因检查以确认其有无先天性疾病;对于存在先天性基因突变的患者,建议行家系筛查,并尽早行造血干细胞移植治疗。     

Moving towards a new era of genomics in the neuronal ceroid lipofuscinoses

The neuronal ceroid lipofuscinoses (NCL) are a group of disorders defined by shared clinical and pathological features, including seizures and progressive decline in vision, neurocognition, and motor functioning, as well as accumulation of autofluorescent lysosomal storage material, or ‘ceroid lipofuscin’. Research has revealed thirteen distinct genetic subtypes. Precisely how the gene mutations lead to the clinical phenotype is still incompletely understood, but recent research progress is starting to shed light on disease mechanisms, in both gene-specific and shared pathways. As the application of new sequencing technologies to genetic disease diagnosis has grown, so too has the spectrum of clinical phenotypes caused by mutations in the NCL genes. Most genes causing NCL have probably been identified, underscoring the need for a shift towards applying genomics approaches to achieve a deeper understanding of the molecular basis of the NCLs and related disorders. Here, we summarize the current understanding of the thirteen identified NCL genes and the proteins they encode, touching upon the spectrum of clinical manifestations linked to each of the genes, and we highlight recent progress leading to a broader understanding of key pathways involved in NCL disease pathogenesis and commonalities with other neurodegenerative diseases.     

高尿酸血症和痛风的遗传学研究进展

痛风是由高尿酸血症引发的一种常见炎性关节炎,受遗传因素和环境因素共同作用。早期研究表明,PRPS1和HPRT1等单基因稀有突变会引起嘌呤合成代谢紊乱,从而引发高尿酸血症和痛风。近年来,全基因组关联分析(Genome-wide association studies,GWAS)已检出多个导致高尿酸血症和痛风的易感位点及相关候选基因。其中SLC2A9、SLC22A11和SLC22A12基因功能缺失性突变可引起遗传性低尿酸血症,而过表达则会加强尿酸的重吸收。ABCG2、SLC17A1和SLC17A3基因功能缺陷型变异会降低肾脏和肠道对尿酸的排泄量。因此,诱发尿酸排泄障碍(高重吸收和低排泄)的基因变异是影响高尿酸血症和痛风的主要遗传因素。另外,抑制-激活生长因子系统、转录因子、细胞骨架以及基因和环境的互作等因素也一定程度影响血液尿酸水平。在中国汉族人群中,两个新发现的易感基因RFX3和KCNQ1可能造成免疫应答受损和胰岛B细胞功能缺陷,从而直接或间接引起高尿酸酸血症和痛风。本文系统综述了高尿酸血症和痛风的遗传学研究,以促进人们对高尿酸血症和痛风发病机理的理解。     

Specific myosin heavy chain mutations suppress troponin I defects in Drosophila muscles

We show that specific mutations in the head of the thick filament molecule myosin heavy chain prevent a degenerative muscle syndrome resulting from the hdp2 mutation in the thin filament protein troponin I. One mutation deletes eight residues from the actin binding loop of myosin, while a second affects a residue at the base of this loop. Two other mutations affect amino acids near the site of nucleotide entry and exit in the motor domain. We document the degree of phenotypic rescue each suppressor permits and show that other point mutations in myosin, as well as null mutations, fail to suppress the hdp2 phenotype. We discuss mechanisms by which the hdp2 phenotypes are suppressed and conclude that the specific residues we identified in myosin are important in regulating thick and thin filament interactions. This in vivo approach to dissecting the contractile cycle defines novel molecular processes that may be difficult to uncover by biochemical and structural analysis. Our study illustrates how expression of genetic defects are dependent upon genetic background, and therefore could have implications for understanding gene interactions in human disease.     

Translational research in myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are receiving unusual attention recently as great strides have been made in understanding the biology. Recognition that excessive cytokine-induced apoptosis plays a significant role in the cytopenias of the majority of patients opened the doors to anti-cytokine therapy, with thalidomide being used with success in approximately 20% patients. Other therapies that have emerged include the thalidomide analog lenalidomide which is particularly beneficial for 5q- patients as well as a subset of non-5q- patients with low or intermediate-1 risk MDS. Other targeted therapies include vitamins, agents that are cytoprotective, differentiation inducers, anti-angiogenic, or immune modulatory. In addition, inhibitors of proteasome, methylation, histone deacetylation, farnesylation, receptor tyrosine kinases, topoisomerase, and matrix mettaloproteinases have yielded encouraging responses in subsets of patients. Specific therapies have also been developed for genetic abnormalities that lead to fusion genes (TEL-PDGFR-beta, or FIP1L1-PDGFR-alpha), or abnormal proteins due to mutations/functional inactivation (FLT3), dysregulated expression (EVI-1). In a short span of ten years, the field has evolved from having no effective therapy to offer the majority of MDS patients save chemotherapy, to having one FDA approved drug, several on the way to approval, and a number of novel agents producing exciting clinical results. This chapter summarizes the novel targets and targeted therapies in the rapidly evolving therapeutic landscape of MDS.     

Downregulation of microRNA-144 inhibits proliferation and promotes the apoptosis of myelodysplastic syndrome cells through the activation of the AKAP12-dependent ERK1/2 signaling pathway

BackgroundMyelodysplastic syndromes (MDS) represent a family of hematopoietic stem cell disorders characterized by ineffective hematopoiesis. While the functions of many microRNAs have been identified in MDS, microRNA-144 (miR-144) remains poorly understood. Thus, the aim of the present study was to determine the effects of miR-144 on cell proliferation and apoptosis in MDS cells and mechanism thereof.MethodsMDS-related microarrays were used for screening differentially expressed genes in MDS. The relationship between miR-144 and A-kinase anchoring protein 12 (AKAP12) was determined by a dual luciferase reporter gene assay. Subsequently, gain- and loss-function approaches were used to assess the effects of miR-144 and AKAP12 on cell proliferation, cell cycle and cell apoptosis by MTT assay and flow cytometry. Following the induction of a mouse model with MDS, the tumor tissues were extract for evaluation of apoptosis and the expression of miR-144, AKAP12, and the relevant genes associated with extracellular-regulated protein kinases 1/2 (ERK1/2) signaling pathway and apoptosis.ResultsWe observed significantly diminished expression of AKAP12 in MDS samples. miR-144 directly bound to AKAP12 3′UTR and reduced its expression in hematopoietic cells. Downregulation of miR-144 or upregulation of AKAP12 was observed to prolong cell cycle, inhibit cell proliferation, and induce apoptosis, accompanied by increased expression of AKAP12, p-ERK1/2, caspase-3, caspase-9, Bax, and p53, as well as decreased expression of Bcl-2. The transplanted tumors in mice with down-regulated miR-144 exhibited a lower mean tumor diameter and weight, and increased apoptosis index and expression of AKAP12 and ERK1/2.ConclusionTaken together, these studies demonstrate the stimulative role of miR-144 in MDS progression by regulating AKAP12-dependent ERK1/2 signaling pathway.