Additive dominant effect of a SOX10 mutation underlies a complex phenotype of PCWH

The value of SOX10 expression in predicting perineural invasion in gastric cancer

BACKGROUND

SRY-related HMG-box 10 (SOX10) protein has a confirmed role in the regulation of neural cell proliferation and differentiation. It is now suggested that the changes in SOX10 expression may be linked to neural invasion by cancer cells. We aimed to assess the value of SOX10 expression in predicting perineural invasion in gastric cancer.

METHODS

A cross-sectional study was performed on 40 patients with gastric cancer. To assess perineural invasion, Hematoxylin & Eosin stained slides were examined. The expression of SOX10 was also examined by immunohistochemistry.

RESULTS

Our study showed higher perineural invasion in those with SOX10 positivity as compared to those without SOX10 expression (64.0% vs. 6.7%, p=0.001). No association was revealed between other baseline variables and SOX10 positivity. The expression of this marker increased the chance of neural invasion up to 17 times as indicated by the multivariable regression modeling. Multivariable regression modeling indicated that the chance of neural invasion increased up to 17 times in cases of SOX10 positivity.

CONCLUSION

Overexpression of SOX10 is closely associated with the risk of perineural invasion in gastric cancer.

Hypolacrimia and Alacrimia as Diagnostic Features for Genetic or Congenital Conditions

As part of the lacrimal apparatus, the lacrimal gland participates in the maintenance of a healthy eye surface by producing the aqueous part of the tear film. Alacrimia and hypolacrimia, which are relatively rare during childhood or young adulthood, have their origin in a number of mechanisms which include agenesia, aplasia, hypoplasia, or incorrect maturation of the gland. Moreover, impaired innervation of the gland and/or the cornea and alterations of protein secretion pathways can lead to a defective tear film. In most conditions leading to alacrimia or hypolacrimia, however, the altered tear film is only one of numerous defects that arise and therefore is commonly disregarded. Here, we have systematically reviewed all of those genetic conditions or congenital disorders that have alacrimia or hypolacrimia as a feature. Where it is known, we describe the mechanism of the defect in question. It has been possible to clearly establish the physiopathology of only a minority of these conditions. As hypolacrimia and alacrimia are rare features, this review could be used as a tool in clinical genetics to perform a quick diagnosis, necessary for appropriate care and counseling.

Three novel variants in SOX10 gene: Waardenburg and PCWH syndromes

Background

Waardenburg syndrome (WS) is a rare genetic disorder characterized by musculoskeletal abnormalities, deafness and hypopigmentation of hair and skin. This article’s aim is to investigate clinical and genetic characteristics of WS in three unrelated Caucasian individuals.

Case presentation

The first patient was a 25-year-old female with congenital bilateral hearing loss, bright-blue-eyes, hypopigmentation of hair and skin, megacolon, language retardation, tenosynovitis and neuromas. The second case was an infant symptomatic from birth, with dysphagia, Hirschsprung disease and neurological abnormalities. The third patient was a 14-year-old boy with congenital bilateral hearing loss and ileocolic Hirschsprung disease. In order to identify variants in potentially causal genes of the patients’ phenotype, genetical testing was conducted: targeted clinical exome, targeted exome and trio exome, respectively. We identified three novel variants spread throughout the coding sequence of SOX10. The c.395C>G variant identified de novo in patient 1 was a single nucleotide substitution in exon 2. The c.850G>T variant identified as heterozygous in patient 2 was a loss-of-function variant that generated a premature stop codon. The c.966dupT variant identified in patient 3 was a duplication that generated a premature stop codon. It had been identified in his father, arising a possible germinal mosaicism. According to in silico predictors the variant identified in patient 1 was considered as pathogenic, whereas the other two were classified as likely pathogenic.

Conclusions

An exact description of the mutations responsible for WS provides useful information to explain clinical features of WS and contributes to better genetic counselling of WS patients.

SOX10: 20 years of phenotypic plurality and current understanding of its developmental function

SOX10 belongs to a family of 20 SRY (sex-determining region Y)-related high mobility group box-containing (SOX) proteins, most of which contribute to cell type specification and differentiation of various lineages. The first clue that SOX10 is essential for development, especially in the neural crest, came with the discovery that heterozygous mutations occurring within and around SOX10 cause Waardenburg syndrome type 4. Since then, heterozygous mutations have been reported in Waardenburg syndrome type 2 (Waardenburg syndrome type without Hirschsprung disease), PCWH or PCW (peripheral demyelinating neuropathy, central dysmyelination, Waardenburg syndrome, with or without Hirschsprung disease), intestinal manifestations beyond Hirschsprung (ie, chronic intestinal pseudo-obstruction), Kallmann syndrome and cancer. All of these diseases are consistent with the regulatory role of SOX10 in various neural crest derivatives (melanocytes, the enteric nervous system, Schwann cells and olfactory ensheathing cells) and extraneural crest tissues (inner ear, oligodendrocytes). The recent evolution of medical practice in constitutional genetics has led to the identification of SOX10 variants in atypical contexts, such as isolated hearing loss or neurodevelopmental disorders, making them more difficult to classify in the absence of both a typical phenotype and specific expertise. Here, we report novel mutations and review those that have already been published and their functional consequences, along with current understanding of SOX10 function in the affected cell types identified through in vivo and in vitro models. We also discuss research options to increase our understanding of the origin of the observed phenotypic variability and improve the diagnosis and medical care of affected patients.

Grandparental genotyping enhances exome variant interpretation

Trio exome sequencing is a powerful tool in the molecular investigation of monogenic disorders and provides an incremental diagnostic yield over proband-only sequencing, mainly due to the rapid identification of de novo disease-causing variants. However, heterozygous variants inherited from unaffected parents may be inadvertently dismissed, although multiple explanations are available for such scenarios including mosaicism in the parent, incomplete penetrance, imprinting, or skewed X-inactivation. We report three probands, in which a pathogenic or likely pathogenic variant was identified upon exome sequencing, yet was inherited from an unaffected parent. Segregation of the variants (in NOTCH1, PHF6, and SOX10) in the grandparent generation revealed that the variant was de novo in each case. Additionally, one proband had skewed X-inactivation. We discuss the possible genetic mechanism in each case, and urge caution in data interpretation of exome sequencing data. We illustrate the utility of expanding segregation studies to the grandparent generation and demonstrate the impact on exome interpretation strategies, by showing that objective genotype data can overcome subjective parental report of lack of symptoms.

Waardenburg syndrome: a rare cause of inherited neuropathy due to SOX10 mutation

Waardenburg syndrome (WS) is a rare disorder comprising sensorineural deafness and pigmentation abnormalities. Four distinct subtypes are defined based on the presence or absence of additional symptoms. Mutations in six genes have been described in WS. SOX10 mutations are usually associated with a more severe phenotype of WS with peripheral demyelinating neuropathy, central dysmyelinating leukodystrophy, and Hirschsprung disease. Here we report a 32-year-old man with a novel heterozygous missense variant in SOX10 gene, who presented with congenital deafness, Hirschsprung disease, iris heterochromia, foot deformity, and intermediate conduction velocity length-dependent sensorimotor neuropathy. This case highlights that the presence of other non-neuropathic features in a patient with presumed hereditary neuropathy should alert the clinician to possible atypical rare causes.

22q11.2q13 duplication including SOX10 causes sex-reversal and peripheral demyelinating neuropathy, central dysmyelinating leukodystrophy, Waardenburg syndrome, and Hirschsprung disease

Diagnosis of genetic syndromes may be difficult when specific components of a disorder manifest at a later age. We present a follow up of a previous report [Seeherunvong et al., (2004); AJMGA 127: 149-151], of an individual with 22q duplication and sex-reversal syndrome. The subject's phenotype evolved to include peripheral and central demyelination, Waardenburg syndrome type IV, and Hirschsprung disease (PCWH; MIM 609136). DNA microarray analysis defined the duplication at 22q11.2q13, including SOX10. Sequencing of the coding region of SOX10 did not reveal any mutations. Our data suggest that SOX10 duplication can cause disorders of sex development and PCWH, supporting the hypothesis that SOX10 toxic gain of function rather than dominant negative activity underlies PCWH.

Transcription factor Sox10 regulates oligodendroglial Sox9 levels via microRNAs

During development of myelin-forming oligodendrocytes in the central nervous system the two closely related transcription factors Sox9 and Sox10 play essential roles that are partly shared and partly unique. Whereas Sox9 primarily functions during oligodendroglial specification, Sox10 is uniquely required to induce terminal differentiation and myelination. During this process, Sox10 protein levels rise substantially. As this coincides with a reciprocal decrease in Sox9, we postulated that Sox10 influences Sox9 amounts in differentiating oligodendrocytes. Here we show that Sox9 levels are indeed inversely coupled to Sox10 levels such that Sox10 deletion in oligodendroglial cells evokes a reciprocal increase in Sox9. We furthermore provide evidence that this coupling involves upregulation of microRNAs miR335 and miR338 as direct transcriptional targets of Sox10. The two microRNAs in turn recognize the 3'-UTR of Sox9 mRNA and may thereby reduce Sox9 protein levels posttranscriptionally in oligodendroglial cells. Such a mechanism may enable oligodendroglial cells to adapt the ratio of both related Sox proteins in a manner required for successful lineage progression and differentiation. Mathematical modeling furthermore shows that the identified regulatory circuit has the potential to convert a transient stimulus into an irreversible switch of cellular properties and may thus contribute to terminal differentiation of oligodendrocytes.

Brain enhancer activities at the gene-poor 5p14.1 autism-associated locus

Due to the vast clinical and genetic heterogeneity, identification of causal genetic determinants for autism spectrum disorder (ASD) has proven to be complex. Whereas several dozen ‘rare’ genetic variants for ASD susceptibility have been identified, studies are still underpowered to analyse ‘common’ variants for their subtle effects. A recent application of genome-wide association studies (GWAS) to ASD indicated significant associations with the single nucleotide polymorphisms (SNPs) on chromosome 5p14.1, located in a non-coding region between cadherin10 (CDH10) and cadherin9 (CDH9). Here we apply an in vivo bacterial artificial chromosome (BAC) based enhancer-trapping strategy in mice to scan the gene desert for spatiotemporal cis-regulatory activities. Our results show that the ASD-associated interval harbors the cortical area, striatum, and cerebellum specific enhancers for a long non-coding RNA, moesin pseudogene1 antisense (MSNP1AS) during the brain developing stages. Mouse moesin protein levels are not affected by exogenously expressed human antisense RNAs in our transgenic brains, demonstrating the difficulty in modeling rather smaller effects of common variants. Our first in vivo evidence for the spatiotemporal transcription of MSNP1AS however provides a further support to connect this intergenic variant with the ASD susceptibility.

Heterozygous deletion at the SOX10 gene locus in two patients from a Chinese family with Waardenburg syndrome type II

OBJECTIVES

Waardenburg syndrome (WS) is a rare disease characterized by sensorineural deafness and pigment disturbance. To date, almost 100 mutations have been reported, but few reports on cases with SOX10 gene deletion. The inheritance pattern of SOX10 gene deletion is still unclear. Our objective was to identify the genetic causes of Waardenburg syndrome type II in a two-generation Chinese family.

METHODS

Clinical evaluations were conducted in both of the patients. Microarray analysis and multiplex ligation-dependent probe amplification (MLPA) were performed to identify disease-related copy number variants (CNVs). DNA sequencing of the SOX10, MITF and SNAI2 genes was performed to identify the pathogenic mutation responsible for WS2.

RESULTS

A 280kb heterozygous deletion at the 22q13.1 chromosome region (including SOX10) was detected in both of the patients. No mutation was found in the patients, unaffected family members and 30 unrelated healthy controls.

CONCLUSIONS

This report is the first to describe SOX10 heterozygous deletions in Chinese WS2 patients. Our result conform the thesis that heterozygous deletions at SOX10 is an important pathogenicity for WS, and present as autosomal dominant inheritance. Nevertheless, heterozygous deletion of the SOX10 gene would be worth investigating to understand their functions and contributions to neurologic phenotypes.