Molecular basis of congenital insensitivity to pain with anhidrosis (CIPA): Mutations and polymorphisms in TRKA (NTRK1) gene encoding the receptor tyrosine kinase for nerve growth factor

Congenital insensitivity to pain with anhidrosis (CIPA), also referred to as hereditary sensory and autonomic neuropathy type IV (HSAN‐IV), is an autosomal recessive hereditary disorder characterized by recurrent episodic fever, anhidrosis (inability to sweat), absence of reaction to noxious stimuli, self‐mutilating behavior, and mental retardation. The TRKA (NTRK1) gene located on chromosome 1 (1q21‐q22), consists of 17 exons and spans at least 23 kb. TRKA encodes the receptor tyrosine kinase (RTK) for nerve growth factor (NGF) and is the gene responsible for CIPA. Defects in NGF signal transduction at the TRKA receptor lead to failure to support survival of sympathetic ganglion neurons and nociceptive sensory neurons derived from the neural crest. Thirty‐seven different TRKA mutations, identified in patients in various countries, including nine frameshift, seven nonsense, seven splice, and 14 missense mutations, are distributed in an extracellular domain involved in NGF binding, as well as in the intracellular signal‐transduction domain. Extensive analysis of CIPA mutations and associated intragenic polymorphisms should facilitate detection of CIPA mutations and aid in the diagnosis and genetic counseling of this painless but severe genetic disorder with devastating complications. In addition, naturally occurring TRKA missense mutations with loss of function provide considerable insight into the structure–function relationship in the RTK family. Further, molecular pathology of CIPA would provide unique opportunities to explore critical roles of the autonomic sympathetic nervous system as well as peripheral sensory nervous system that transmit noxious stimuli in humans. Hum Mutat 18:462–471, 2001. © 2001 Wiley‐Liss, Inc.     

先天性无痛无汗症1例并文献复习

报告2018年10月收治的1例先天性无痛无汗症,患者年龄32 d,采集患儿及其父母外周血进行医学外显子 5 000种疾病筛查,并对候选基因变异进行Sanger测序验证。患儿主要临床表现为无痛、无汗、反复发热。基因分子遗 传学分析结果提示在患儿遗传性感觉和自主神经病4型等疾病相关基因神经营养因子酪氨酸激酶受体1型(neurotrophic tyrosine kinase receptor type 1,NTRK1)中存在复合杂合突变(c.36G>A和c.851-33T>A)。结果显示两个突变分别来自父母 双方。c.851-33T>A为既往已报道致病突变,c.36G>A为未报道的突变,该突变可导致色氨酸转变成终止密码子。对于 无明确致病报道的点突变,进一步参考美国医学遗传学和基因组学学院(ACMG)基因突变解读指南,评估其为致病基 因,生物学危害性为可能有害。先天性无痛无汗症临床罕见,该病为单基因遗传病,基因分子遗传学分析有助于诊 断及发现新的基因突变。     

Genetics of serum BDNF: Meta-analysis of the Val66Met and genome-wide association study

Abstract

Objectives. Lower levels of serum brain derived neurotrophic factor (BDNF) is one of the best known biomarkers of depression. To identify genetic variants associated with serum BDNF, we tested the Val66Met (rs6265) functional variant and conducted a genome-wide association scan (GWAS). Methods. In a community-based sample (N = 2054; aged 19–101, M = 51, SD = 15) from Sardinia, Italy, we measured serum BDNF concentration and conducted a GWAS. Results. We estimated the heritability of serum BDNF to be 0.48 from sib-pairs. There was no association between serum BDNF and Val66Met in the SardiNIA sample and in a meta-analysis of published studies (k = 13 studies, total n = 4727, P = 0.92). Although no genome-wide significant associations were identified, some evidence of association was found in the BDNF gene (rs11030102, P = 0.001) and at two loci (rs7170215, P = 4.8 × 10^–5 and rs11073742 P = 1.2 × 10^–5) near and within NTRK3 gene, a neurotrophic tyrosine kinase receptor. Conclusions. Our study and meta-analysis of the literature indicate that the BDNF Val66Met variant is not associated with serum BDNF, but other variants in the BDNF and NTRK3 genes might regulate the level of serum BDNF.     

Infantile Fibrosarcoma With NTRK3–ETV6 Fusion Successfully Treated With the Tropomyosin‐Related Kinase Inhibitor LOXO‐101

Infantile fibrosarcoma (IFS) is a rare pediatric cancer typically presenting in the first 2 years of life. Surgical resection is usually curative and chemotherapy is active against gross residual disease. However, when recurrences occur, therapeutic options are limited. We report a case of refractory IFS with constitutive activation of the tropomyosin‐related kinase (TRK) signaling pathway from an ETS variant gene 6–neurotrophin 3 receptor gene (ETV6–NTRK3) gene fusion. The patient enrolled in a pediatric Phase 1 trial of LOXO‐101, an experimental, highly selective inhibitor of TRK. The patient experienced a rapid, radiographic response, demonstrating the potential for LOXO‐101 to provide benefit for IFS harboring NTRK gene fusions.     

Emerging soft tissue tumors with kinase fusions: An overview of the recent literature with an emphasis on diagnostic criteria

A recent breakthrough in the classification of soft tissue tumors (STT) has been a significant expansion in the number of neoplasms associated with NTRK and other kinase related fusions. This is important not only for diagnostic purposes, but also because it opens new avenues for targeted therapy. Indeed, recent clincal trials have shown significant benefit across multiple tumor‐types, prompting approval of NTRK inhibitors for clinical use in the setting of advanced/metastatic NTRK‐rearranged neoplasms. Despite these therapeutic oportunities, diagnostic challenges have transpired in recognizing these emerging new histologic subtypes of kinase fusions positive‐STT prospectively. This, in part, is attributable to their wide morphologic spectrum, variable risk of malignancy, and non‐specific immunoprofile. As such, recommendations for pathologic criteria and immunohistochemical testing are needed to improve classification and streamline the small subset of potential candidates for further molecular validation. This overview summarizes the key histologic features of various STT associated with NTRK and other kinase fusions, which appear to share a similar morphologic spectrum. Immunohistochemically, many of these tumors, regardless of the kinase fusion type, notably show co‐expression of S100 and CD34; issues related to the utility of pan‐NTRK and NTRK1 immunostaining are therefore summarized. Finally, I discuss the role of confirmatory molecular testing and how, in some instances, this may also be of prognostic value. This review is intended as a critical summary of the current literature to emphasize pathologic criteria for improving recognition of this emerging and complex group of kinase fusion associated STT.     

A Novel Point Variant in NTRK3, R645C, Suggests a Role of this Gene in the Pathogenesis of Hirschsprung Disease

Hirschsprung disease (HSCR) is a developmental disorder characterized by the absence of ganglion cells in the myenteric and submucosal plexuses due to a defect in the migration process of neural crest neuroblasts. Manifestation of the disease has been linked to the dysfunction of two principal signalling pathways involved in the enteric nervous system (ENS) formation: the RET-GDNF and the EDN3-EDNRB receptor systems. However, the NTF3/NTRK3 signalling pathway plays an essential role in the development of the ENS suggesting a potential role for those genes in the pathogenesis of HSCR. We have sought to evaluate the candidature of the NTRK3 gene, which encodes the TrkC receptor, as a susceptibility gene for Hirschsprung disease. Using dHPLC technology we have screened the NTRK3 coding region in 143 Spanish HSCR patients. A total of four previously described polymorphisms and 12 novel sequence variants were detected. Of note, the novel R645C mutation was detected in 2 affected siblings of a HSCR family also carrying a RET splicing mutation. Using bioinformatics tools we observed that the presence of an additional cysteine residue might implicate structural alterations in the mutated protein. We propose haploinsufficiency as the most probable mechanism for the NTRK3 R645C mutation. NTRK3 and RET mutations in this family only appear together in the HSCR patients, suggesting that they per se are necessary but not sufficient to produce the phenotype. In addition, it is quite probable that the contribution of other still unidentified modifier genes, may be responsible for the different phenotypes (length of aganglionosis) in the two affected members.     

Incorporating traditional and emerging biomarkers in the clinical management of metastatic colorectal cancer: an update

ABSTRACT

Introduction

Molecular profiling has led to significantly longer survival in metastatic colorectal cancer (mCRC) patients. Clinical guidelines recommend testing for KRAS/NRAS, BRAF and MSI status, and new biomarkers such as HER2 amplification and NTRK fusions have emerged more recently in refractory CRC, supported by overwhelming clinical relevance. These biomarkers can guide treatment management to improve clinical outcomes in these patients.