A novel TUFM homozygous variant in a child with mitochondrial cardiomyopathy expands the phenotype of combined oxidative phosphorylation deficiency 4

Identification of key genes regulating brown adipose tissue thermogenesis in goat kids (Capra hircus) by using weighted gene co-expression network analysis

Brown adipose tissue (BAT) is crucial for the maintenance of body temperature in newborn animals through non-shivering thermogenesis (NST). However, which kind key genes involved in the regulation of BAT thermogenesis and the internal regulation mechanism of heat production in goat BAT were still unclear. In this study, we analyzed the perirenal adipose tissue transcriptome of Dazu black goats from 0, 7, 14, 21 and 28 days after birth using weighted gene co-expression network analysis (WGCNA) to identify key genes involved in the thermogenesis of BAT. Genes were classified into 22 co-expression modules by WGCNA. The turquoise module exhibited high gene expression in D0, with generally lower expression in the later dates. This pattern is consistent with the rapid color, morphological, and thermogenic changes observed in perirenal adipose tissue shortly after birth. GO functional annotation revealed that the genes in the turquoise module were significantly enriched in the mitochondrion, mitochondrial protein-containing complex, cytoplasm, and mitochondrial inner membrane. KEGG pathway enrichment analysis indicated that these genes were predominantly enriched in the signaling pathways of oxidative phosphorylation, thermogenesis, and TCA cycle. By combining the gene co-expression network analysis of the turquoise module genes and the differentially expression genes (DEG) analysis, we identified 5 candidate key genes (ACO2, MRPS27, IMMT, MRPL12, and TUFM) involved in regulation of perirenal adipose tissue thermogenesis. This finding offer candidate genes that in the regulation of BAT thermogenesis and body temperature maintenance in goat kids.

Emerging mechanisms of human mitochondrial translation regulation

Mitochondrial translation regulation enables precise control over the synthesis of hydrophobic proteins encoded by the organellar genome, orchestrating their membrane insertion, accumulation, and assembly into oxidative phosphorylation (OXPHOS) complexes. Recent research highlights regulation across all translation stages (initiation, elongation, termination, and recycling) through a complex interplay of mRNA structures, specialized translation factors, and unique regulatory mechanisms that adjust protein levels for stoichiometric assembly. Key discoveries include mRNA-programmed ribosomal pausing, frameshifting, and termination-dependent re-initiation, which fine-tune protein synthesis and promote translation of overlapping open reading frames (ORFs) in bicistronic transcripts. In this review, we examine these advances, which are significantly enhancing our understanding of mitochondrial gene expression.

A zebrafish tufm mutant model for the COXPD4 syndrome of aberrant mitochondrial function

Mitochondrial dysfunction is a critical factor leading to a wide range of clinically heterogeneous and often severe disorders due to its central role in generating cellular energy. Mutations in the TUFM gene are known to cause combined oxidative phosphorylation deficiency 4 (COXPD4), a rare mitochondrial disorder characterized by a comprehensive quantitative deficiency in mitochondrial respiratory chain (MRC) complexes. The development of a reliable animal model for COXPD4 is crucial for elucidating the roles and mechanisms of TUFM in disease pathogenesis and benefiting its medical management. In this study, we construct a zebrafish tufm-/- mutant that closely resembles the COXPD4 syndrome, exhibiting compromised mitochondrial protein translation, dysfunctional mitochondria with oxidative phosphorylation defects, and significant metabolic suppression of the tricarboxylic acid cycle. Leveraging this COXPD4 zebrafish model, we comprehensively validate the clinical relevance of TUFM mutations and identify probucol as a promising therapeutic approach for managing COXPD4. Our data offer valuable insights for understanding mitochondrial diseases and developing effective treatments.

Whole exome sequencing in energy deficiency inborn errors of metabolism: A systematic review

Broad biochemical complexity and frequent overlapping clinical symptoms of inborn errors of metabolism (IEM), especially in energy-deficient patients, make accurate diagnosis difficult. In recent years, whole exome sequencing (WES), a comprehensive protein coding genetic test, has been used to diagnose patients at the molecular level. This study aims to evaluate the potential of WES in diagnosing energy-deficient IEM patients with limited biochemical findings and to identify common symptoms patterns in reported cases. Articles were identified using a combination of search terms in online databases (Science Direct, PubMed Central and Wiley). English-language case reports citing WES in the diagnosis of energy-deficient IEM patients were reviewed. This systematic review was conducted and reported using the 'Preferred Reporting Items for Systematic Reviews and Meta-Analyses' checklist. The quality and risk of bias were assessed using Joanna Briggs Institute critical appraisal tool. A total of 37 studies comprising of 54 case reports were included in this review. The median age of the patients was 0.4 years, with 55.6% being male and 44.4% being female. A total of 33 mutant genes were reported and they related to either metabolism or mitochondrial function. WES was able to identify mutations in 53 of 54 cases reported. The diagnosis of energy-deficient IEM patients is crucial, particularly given the challenging range of diverse clinical symptoms they present. The high accuracy of the WES technique appears to improve the diagnostic process. Further research defining more detailed guidelines is needed to engage with this rare set of genetic diseases.

Prenatal phenotypes and pregnancy outcomes of fetuses with 16p11.2 microdeletion/microduplication

BACKGROUND

Chromosomal 16p11.2 deletions and duplications are genomic disorders which are characterized by neurobehavioral abnormalities, obesity, congenital abnormalities. However, the prenatal phenotypes associated with 16p11.2 copy number variations (CNVs) have not been well characterized. This study aimed to provide an elaborate summary of intrauterine phenotypic features for these genomic disorders.

METHODS

Twenty prenatal amniotic fluid samples diagnosed with 16p11.2 microdeletions/microduplications were obtained from pregnant women who opted for invasive prenatal testing. Karyotypic analysis and chromosomal microarray analysis (CMA) were performed in parallel. The pregnancy outcomes and health conditions of all cases after birth were followed up. Meanwhile, we made a pooled analysis of the prenatal phenotypes in the published cases carrying 16p11.2 CNVs.

RESULTS

20 fetuses (20/20,884, 0.10%) with 16p11.2 CNVs were identified: five had 16p11.2 BP2-BP3 deletions, 10 had 16p11.2 BP4-BP5 deletions and five had 16p11.2 BP4-BP5 duplications. Abnormal ultrasound findings were recorded in ten fetuses with 16p11.2 deletions, with various degrees of intrauterine phenotypic features observed. No ultrasound abnormalities were observed in any of the 16p11.2 duplications cases during the pregnancy period. Eleven cases with 16p11.2 deletions terminated their pregnancies. For 16p11.2 duplications, four cases gave birth to healthy neonates except for one case that was lost to follow-up.

CONCLUSIONS

Diverse prenatal phenotypes, ranging from normal to abnormal, were observed in cases with 16p11.2 CNVs. For 16p11.2 BP4-BP5 deletions, abnormalities of the vertebral column or ribs and thickened nuchal translucency were the most common structural and non-structural abnormalities, respectively. 16p11.2 BP2-BP3 deletions might be closely associated with fetal growth restriction and single umbilical artery. No characteristic ultrasound findings for 16p11.2 duplications have been observed to date. Given the variable expressivity and incomplete penetrance of 16p11.2 CNVs, long-term follow-up after birth should be conducted for these cases.

A very rare presentation of mitochondrial elongation factor Tu deficiency-TUFM mutation and literature review

OBJECTIVES

The mitochondrial elongation factor Tu (EF-Tu), encoded by the TUFM gene, is a GTPase, which is part of the mitochondrial protein translation mechanism. If it is activated, it delivers the aminoacyl-tRNAs to the mitochondrial ribosome. Here, a patient was described with a homozygous missense variant in the TUFM [c.1016G>A (p.Arg339Gln)] gene. To date, only six patients have been reported with bi-allelic pathogenic variants in TUFM, leading to combined oxidative phosphorylation deficiency 4 (COXPD4) characterized by severe early-onset lactic acidosis, encephalopathy, and cardiomyopathy.

CASE PRESENTATION

The patient presented here had the phenotypic features of TUFM-related disease, lactic acidosis, hypotonia, liver dysfunction, optic atrophy, and mild encephalopathy.

CONCLUSIONS

We aimed to expand the clinical spectrum of pathogenic variants of TUFM.

Molecular pathways in mitochondrial disorders due to a defective mitochondrial protein synthesis

Mitochondria play a central role in cellular metabolism producing the necessary ATP through oxidative phosphorylation. As a remnant of their prokaryotic past, mitochondria contain their own genome, which encodes 13 subunits of the oxidative phosphorylation system, as well as the tRNAs and rRNAs necessary for their translation in the organelle. Mitochondrial protein synthesis depends on the import of a vast array of nuclear-encoded proteins including the mitochondrial ribosome protein components, translation factors, aminoacyl-tRNA synthetases or assembly factors among others. Cryo-EM studies have improved our understanding of the composition of the mitochondrial ribosome and the factors required for mitochondrial protein synthesis and the advances in next-generation sequencing techniques have allowed for the identification of a growing number of genes involved in mitochondrial pathologies with a defective translation. These disorders are often multisystemic, affecting those tissues with a higher energy demand, and often present with neurodegenerative phenotypes. In this article, we review the known proteins required for mitochondrial translation, the disorders that derive from a defective mitochondrial protein synthesis and the animal models that have been established for their study.

Illuminating mitochondrial translation through mouse models

Mitochondria are hubs of metabolic activity with a major role in ATP conversion by oxidative phosphorylation (OXPHOS). The mammalian mitochondrial genome encodes 11 mRNAs encoding 13 OXPHOS proteins along with 2 rRNAs and 22 tRNAs, that facilitate their translation on mitoribosomes. Maintaining the internal production of core OXPHOS subunits requires modulation of the mitochondrial capacity to match the cellular requirements and correct insertion of particularly hydrophobic proteins into the inner mitochondrial membrane. The mitochondrial translation system is essential for energy production and defects result in severe, phenotypically diverse diseases, including mitochondrial diseases that typically affect postmitotic tissues with high metabolic demands. Understanding the complex mechanisms that underlie the pathologies of diseases involving impaired mitochondrial translation is key to tailoring specific treatments and effectively targeting the affected organs. Disease mutations have provided a fundamental, yet limited, understanding of mitochondrial protein synthesis, since effective modification of the mitochondrial genome has proven challenging. However, advances in next generation sequencing, cryoelectron microscopy, and multi-omic technologies have revealed unexpected and unusual features of the mitochondrial protein synthesis machinery in the last decade. Genome editing tools have generated unique models that have accelerated our mechanistic understanding of mitochondrial translation and its physiological importance. Here we review the most recent mouse models of disease pathogenesis caused by defects in mitochondrial protein synthesis and discuss their value for preclinical research and therapeutic development.

Unusual Trisomy X Phenotype Associated with a Concurrent Heterozygous 16p11.2 Deletion: Importance of an Integral Approach for Proper Diagnosis

Trisomy X is the most frequent sex chromosome anomaly in women, but it is often underdiagnosed postnatally because most patients do not show any clinical manifestation. It is estimated that only 10% of patients with trisomy X are diagnosed by clinical findings. Thus, it has been proposed that the clinical spectrum is not yet fully delimited, and additional uncommon or atypical clinical manifestations could be related to this entity. The present report describes a female carrying trisomy X but presenting atypical manifestations, including severe intellectual disability, short stature, thymus hypoplasia, and congenital hypothyroidism (CH). These clinical findings were initially attributed to trisomy X. However, chromosome microarray analysis (CMA) subsequently revealed that the patient also bears a heterozygous 304-kb deletion at 16p11.2. This pathogenic copy-number variant (CNV) encompasses 13 genes, including TUFM. Some authors recommend that when a phenotype differs from that described for an identified microdeletion, the presence of pathogenic variants in the non-deleted allele should be considered to assess for an autosomal recessive disorder; thus, we used a panel of 697 genes to rule out a pathogenic variant in the non-deleted TUFM allele. We discuss the possible phenotypic modifications that might be related to an additional CNV in individuals with sex chromosome aneuploidy (SCA), as seen in our patient. The presence of karyotype-demonstrated trisomy X and CMA-identified 16p11.2 deletion highlights the importance of always correlating a patient's clinical phenotype with the results of genetic studies. When the phenotype includes unusual manifestations and/or exhibits discrepancies with that described in the literature, as exemplified by our patient, a more extensive analysis should be undertaken to enable a correct diagnosis that will support proper management, genetic counseling, and medical follow-up.

GATD3A, a mitochondrial deglycase with evolutionary origins from gammaproteobacteria, restricts the formation of advanced glycation end products

BACKGROUND

Functional complexity of the eukaryotic mitochondrial proteome is augmented by independent gene acquisition from bacteria since its endosymbiotic origins. Mammalian homologs of many ancestral mitochondrial proteins have uncharacterized catalytic activities. Recent forward genetic approaches attributed functions to proteins in established metabolic pathways, thereby limiting the possibility of identifying novel biology relevant to human disease. We undertook a bottom-up biochemistry approach to discern evolutionarily conserved mitochondrial proteins with catalytic potential.

RESULTS

Here, we identify a Parkinson-associated DJ-1/PARK7-like protein-glutamine amidotransferase-like class 1 domain-containing 3A (GATD3A), with bacterial evolutionary affinities although not from alphaproteobacteria. We demonstrate that GATD3A localizes to the mitochondrial matrix and functions as a deglycase. Through its amidolysis domain, GATD3A removes non-enzymatic chemical modifications produced during the Maillard reaction between dicarbonyls and amines of nucleotides and amino acids. GATD3A interacts with factors involved in mitochondrial mRNA processing and translation, suggestive of a role in maintaining integrity of important biomolecules through its deglycase activity. The loss of GATD3A in mice is associated with accumulation of advanced glycation end products (AGEs) and altered mitochondrial dynamics.

CONCLUSIONS

An evolutionary perspective helped us prioritize a previously uncharacterized but predicted mitochondrial protein GATD3A, which mediates the removal of early glycation intermediates. GATD3A restricts the formation of AGEs in mitochondria and is a relevant target for diseases where AGE deposition is a pathological hallmark.

Bi-allelic variants in neuronal cell adhesion molecule cause a neurodevelopmental disorder characterized by developmental delay, hypotonia, neuropathy/spasticity

Cell adhesion molecules are membrane-bound proteins predominantly expressed in the central nervous system along principal axonal pathways with key roles in nervous system development, neural cell differentiation and migration, axonal growth and guidance, myelination, and synapse formation. Here, we describe ten affected individuals with bi-allelic variants in the neuronal cell adhesion molecule NRCAM that lead to a neurodevelopmental syndrome of varying severity; the individuals are from eight families. This syndrome is characterized by developmental delay/intellectual disability, hypotonia, peripheral neuropathy, and/or spasticity. Computational analyses of NRCAM variants, many of which cluster in the third fibronectin type III (Fn-III) domain, strongly suggest a deleterious effect on NRCAM structure and function, including possible disruption of its interactions with other proteins. These findings are corroborated by previous in vitro studies of murine Nrcam-deficient cells, revealing abnormal neurite outgrowth, synaptogenesis, and formation of nodes of Ranvier on myelinated axons. Our studies on zebrafish nrcama^Δ mutants lacking the third Fn-III domain revealed that mutant larvae displayed significantly altered swimming behavior compared to wild-type larvae (p < 0.03). Moreover, nrcama^Δ mutants displayed a trend toward increased amounts of α-tubulin fibers in the dorsal telencephalon, demonstrating an alteration in white matter tracts and projections. Taken together, our study provides evidence that NRCAM disruption causes a variable form of a neurodevelopmental disorder and broadens the knowledge on the growing role of the cell adhesion molecule family in the nervous system.

2,2',4,4'-Tetrabromodiphenyl ether disrupts spermatogenesis in mice by interfering with the ER-Nrf1-Tfam-mitochondria pathway

2,2',4,4' -tetrabromodiphenyl ether (BDE47), a well-known endocrine disruptor of the estrogen receptor (ER) is toxic to the mitochondria and spermatogenesis. This study aimed to explore the mechanism of BDE47 on spermatogenesis in mammals. Adult male Institute of Cancer Research (ICR) mice were gavaged daily with BDE47 (0, 1, or 10 mg/kg bw) for 8 weeks. Testicular weight, sperm production and motility, morphology of spermatogenic cells, nuclear respiratory factor 1 (Nrf1) level, and its expression in testes were determined. In vitro, cell viability, and key molecules in the ER-Nrf1-mitochondrial transcription factor A (Tfam)-mitochondria pathway in the immortalized mouse spermatogonia line (GC1) were determined at 48 h and 0-5 h after exposure; RNA interference (RNAi) was also performed to verify that the decreased Nrf1 was associated with mitochondrial dysfunction and the impaired viability of germ cells. The results indicated that BDE47 impaired testis weight and spermatogenesis, impaired mitochondria and germ cells, and decreased Nrf1 in the testes of mice. In vitro, after 48 h exposure, BDE47 reduced cell viability, Nrf1 protein, and mRNA of Nrf1, Tfam, ATP synthase subunit β (Atp5b), and cytochrome c oxidase subunit I (mt-CO1) in GC1 while also reducing mRNA of Nrf1 and Tfam promptly (from 1 to 5 h) after exposure. Furthermore, Nrf1 RNA interference decreased viability and mitochondrial function in GC1. These results indicated that BDE47 disrupts spermatogenesis in mice, probably by interfering with the ER-Nrf1-Tfam-mitochondria pathway, and Nrf1 is a target molecule of BDE47 estrogen receptor.

A functional genomics pipeline identifies pleiotropy and cross-tissue effects within obesity-associated GWAS loci

Genome-wide association studies (GWAS) have identified many disease-associated variants, yet mechanisms underlying these associations remain unclear. To understand obesity-associated variants, we generate gene regulatory annotations in adipocytes and hypothalamic neurons across cellular differentiation stages. We then test variants in 97 obesity-associated loci using a massively parallel reporter assay and identify putatively causal variants that display cell type specific or cross-tissue enhancer-modulating properties. Integrating these variants with gene regulatory information suggests genes that underlie obesity GWAS associations. We also investigate a complex genomic interval on 16p11.2 where two independent loci exhibit megabase-range, cross-locus chromatin interactions. We demonstrate that variants within these two loci regulate a shared gene set. Together, our data support a model where GWAS loci contain variants that alter enhancer activity across tissues, potentially with temporally restricted effects, to impact the expression of multiple genes. This complex model has broad implications for ongoing efforts to understand GWAS.

TUFM is involved in Alzheimer's disease-like pathologies that are associated with ROS

Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-β precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of β-amyloid protein (Aβ) and β-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.

Mitochondrial Protein Translation: Emerging Roles and Clinical Significance in Disease

Mitochondria are one of the most important organelles in cells. Mitochondria are semi-autonomous organelles with their own genetic system, and can independently replicate, transcribe, and translate mitochondrial DNA. Translation initiation, elongation, termination, and recycling of the ribosome are four stages in the process of mitochondrial protein translation. In this process, mitochondrial protein translation factors and translation activators, mitochondrial RNA, and other regulatory factors regulate mitochondrial protein translation. Mitochondrial protein translation abnormalities are associated with a variety of diseases, including cancer, cardiovascular diseases, and nervous system diseases. Mutation or deletion of various mitochondrial protein translation factors and translation activators leads to abnormal mitochondrial protein translation. Mitochondrial tRNAs and mitochondrial ribosomal proteins are essential players during translation and mutations in genes encoding them represent a large fraction of mitochondrial diseases. Moreover, there is crosstalk between mitochondrial protein translation and cytoplasmic translation, and the imbalance between mitochondrial protein translation and cytoplasmic translation can affect some physiological and pathological processes. This review summarizes the regulation of mitochondrial protein translation factors, mitochondrial ribosomal proteins, mitochondrial tRNAs, and mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) in the mitochondrial protein translation process and its relationship with diseases. The regulation of mitochondrial protein translation and cytoplasmic translation in multiple diseases is also summarized.

A novel truncating variant in the FGD1 gene associated with Aarskog-Scott syndrome in a family previously diagnosed with Tel Hashomer camptodactyly

Tel Hashomer camptodactyly syndrome is a long-known entity characterized by camptodactyly with muscular hypoplasia, skeletal dysplasia, and abnormal palmar creases. Currently, the genetic basis for this disorder is unknown, thus there is a possibility that this clinical presentation may be contained within another genetic diagnosis. Here, we present a multiplex family with a previous clinical diagnosis of Tel Hashomer camptodactyly syndrome. Whole exome sequencing and pedigree-based analysis revealed a novel hemizygous truncating variant c.269_270dup (p.Phe91Alafs*34) in the FGD1 gene (NM_004463.3) in all three symptomatic patients, congruous with a diagnosis of Aarskog-Scott syndrome. Our report adds to the limited data on Aarskog-Scott syndrome, and emphasizes the importance of unbiased comprehensive molecular testing toward establishing a diagnosis for genetic syndromes with unknown genetic basis.

A recurring NFS1 pathogenic variant causes a mitochondrial disorder with variable intra-familial patient outcomes

Iron‑sulfur clusters (FeSCs) are vital components of a variety of essential proteins, most prominently within mitochondrial respiratory chain complexes I-III; Fe-S assembly and distribution is performed via multi-step pathways. Variants affecting several proteins in these pathways have been described in genetic disorders, including severe mitochondrial disease. Here we describe a Christian Arab kindred with two infants that died due to mitochondrial disorder involving Fe-S containing respiratory chain complexes and a third sibling who survived the initial crisis. A homozygous missense variant in NFS1: c.215G>A; p.Arg72Gln was detected by whole exome sequencing. The NFS1 gene encodes a cysteine desulfurase, which, in complex with ISD11 and ACP, initiates the first step of Fe-S formation. Arginine at position 72 plays a role in NFS1-ISD11 complex formation; therefore, its substitution with glutamine is expected to affect complex stability and function. Interestingly, this is the only pathogenic variant ever reported in the NFS1 gene, previously described once in an Old Order Mennonite family presenting a similar phenotype with intra-familial variability in patient outcomes. Analysis of datasets from both populations did not show a common haplotype, suggesting this variant is a recurrent de novo variant. Our report of the second case of NFS1-related mitochondrial disease corroborates the pathogenicity of this recurring variant and implicates it as a hot-spot variant. While the genetic resolution allows for prenatal diagnosis for the family, it also raises critical clinical questions regarding follow-up and possible treatment options of severely affected and healthy homozygous individuals with mitochondrial co-factor therapy or cysteine supplementation.

A novel composition of two heterozygous GFM1 mutations in a Chinese child with epilepsy and mental retardation

INTRODUCTION

G elongation factor mitochondrial 1 (GFM1) encodes one of the mitochondrial translation elongation factors. GFM1 variants were reported to be associated with neurological diseases and liver diseases in a few cases. Here, we present a novel composition of two heterozygous mutations of GFM1 in a boy with epilepsy, mental retardation, and other unusual phenotypes.

METHODS

The patient was found to be blind and experienced recurrent convulsive seizures such as nodding and hugging at the age of 3 months. After antiepileptic treatment with topiramate, he had no obvious seizures but still had mental retardation. The patient vomited frequently at 16 months old, sometimes accompanied by epileptic seizures. Hematuria metabolic screening, mutation screening of mitochondrial gene, and mitochondrial nuclear gene were negative. Then, he was analyzed by whole-exome sequencing (WES).

RESULTS

Whole-exome sequencing revealed a novel composition of two heterozygous mutations in GFM1, the maternal c.679G > A (has not been reported) and the paternal c.1765-1_1765-2del (previously reported). At present, there is no specific and effective treatment for the disease, and the prognosis is very poor.

CONCLUSION

The discovery of new phenotypes and new genotypes will further enrich the diagnosis information of the disease and provide more experiences for clinicians to quickly diagnose the disease and judge the prognosis.

TUFM-knockdown inhibits the migration and proliferation of gastrointestinal stromal tumor cells

Gastrointestinal stromal tumors (GISTs) are the most common pathologic type of mesenchymal tumor in the digestive tract. Patients with GIST face the risk of metastasis, postoperative recurrence and imatinib mesylate (IM) resistance. Mitochondrial Tu translation elongation factor (TUFM) is highly expressed in GISTs, and is associated with oncogenesis, progression and prognosis. There is evidence that TUFM is involved in tumor invasion and metastasis. However, the effect of TUFM on GIST-T1 cells and the IM-resistant GIST-IR cell line remains unclear. The present study aimed to evaluate the effects of TUFM on the proliferation, migration and apoptosis of GIST cells in vitro. TUFM short hairpin (sh)RNA expression plasmids were transfected into GIST-T1 and GIST-IR cells by electroporation. The expression levels of enhanced green fluorescent protein were observed by fluorescence microscopy to evaluate the electroporation efficiency. The expression levels of TUFM were detected by western blot analysis and reverse transcription-quantitative PCR. Cell proliferation was assessed by counting cells and using a Cell Counting Kit-8 assay. Cell migration was analyzed using wound healing and Transwell migration assays. Cell cycle distribution and late apoptosis were assessed by flow cytometry. TUFM shRNA expression plasmids were successfully transfected into the GIST cell line by electroporation. The transfection efficiency was >75%, and the TUFM gene silencing efficiency was 73.2±1.4%. TUFM-knockdown decreased the proliferation and migration capacity of GIST-T1 and GIST-IR cells. The proportion of cells in the pre-G1 stage was increased without change in the proportions of cells in the G₁, S and G₂/M stages after TUFM silencing in GIST-T1 and GIST-IR cells. TUFM may be related to GIST infiltration and metastatic recurrence, suggesting that TUFM may be an effective target for preventing the progression and metastasis of GISTs.

A novel mutation in MYCN gene causing congenital absence of the flexor pollicis longus tendon as an unusual presentation of Feingold syndrome 1

Feingold syndrome 1 (FGLDS1) is an autosomal dominant malformation syndrome, characterized by skeletal anomalies, microcephaly, facial dysmorphism, gastrointestinal atresias and learning disabilities. Mutations in the MYCN gene are known to be the cause of this syndrome. Congenital absence of the flexor pollicis longus (CAFPL) tendon is a rare hand anomaly. Most cases are sporadic and no genetic variants have been described associated with this abnormality. We describe here a pedigree combining familial CAFPL tendon as a feature of FGLDS1. Molecular analyses of whole exome sequence data in five affected family members spanning three generations of this family revealed a novel mutation in the MYCN gene (c.1171C>T; p.Arg391Cys). Variants in MYCN have not been published in association with isolated or syndromic CAFPL tendon, nor has this been described as a skeletal feature of Feingold syndrome. This report expands on the clinical and molecular spectrum of MYCN-related disorders and highlights the importance of MYCN protein in normal human thumb and foramen development.

Genetic aspects of the oxidative phosphorylation dysfunction in dilated cardiomyopathy

Dilated cardiomyopathy is a frequent and extremely heterogeneous medical condition. Deficits in the oxidative phosphorylation system have been described in patients suffering from dilated cardiomyopathy. Hence, mutations in proteins related to this biochemical pathway could be etiological factors for some of these patients. Here, we review the clinical phenotypes of patients harboring pathological mutations in genes related to the oxidative phosphorylation system, either encoded in the mitochondrial or in the nuclear genome, presenting with dilated cardiomyopathy. In addition to the clinical heterogeneity of these patients, the large genetic heterogeneity has contributed to an improper allocation of pathogenicity for many candidate mutations. We suggest criteria to avoid incorrect assignment of pathogenicity to newly found mutations and discuss possible therapies targeting the oxidative phosphorylation function.

A novel heterozygous loss-of-function DCC Netrin 1 receptor variant in prenatal agenesis of corpus callosum and review of the literature

Agenesis of the corpus callosum (ACC) is a common prenatally-detected brain anomaly. Recently, an association between mutations in the DCC Netrin 1 receptor (DCC) gene and ACC, with or without mirror movements, has been demonstrated. In this manuscript, we present a family with a novel heterozygous frameshift mutation in DCC, review the available literature, and discuss the challenges involved in the genetic counseling for recently discovered disorders with paucity of medical information. We performed whole exome sequencing in a healthy nonconsanguineous couple that underwent two pregnancy terminations due to prenatal diagnosis of ACC. A heterozygous variant c.2774dupA (p.Asn925Lysfs*17) in the DCC gene was demonstrated in fetal and paternal DNA samples, as well as in a healthy 4-year-old offspring. When directly questioned, both father and child reported having mirror movements not affecting quality of life. Segregation analysis demonstrated the variant in three paternal siblings, two of them having mirror movements. Brain imaging revealed normal corpus callosum. Summary of literature data describing heterozygous loss-of-function variants in DCC (n = 61) revealed 63.9% penetrance for mirror movements, 9.8% for ACC, and 5% for both. No significant neurodevelopmental abnormalities were reported among the seven published patients with DCC loss-of-function variants and ACC. Prenatal diagnosis of ACC should prompt a specific anamnesis regarding any neurological disorder, as well as intentional physical examination of both parents aimed to detect mirror movements. In suspicious cases, detection of DCC pathogenic variants might markedly improve the predicted prognosis, alleviate the parental anxiety, and possibly prevent pregnancy termination.