Pre-implantation genetic diagnosis in an Iranian family with a novel mutation in MUT gene

Background

Methylmalonic acidemia (MMA), which is an autosomal recessive metabolic disorder, is caused by mutations in methylmalonyl-CoA mutase (MUT) gene. As a result, the conversion of methylmalonyl-CoA to succinyl-CoA is impaired in this disorder, leading to a wide range of clinical manifestations varying from no signs or symptoms to severe lethargy and metabolic crisis in newborn infants. Since identification of novel mutations in MUT gene can help discover the exact pathogenesis of MMA and also use these disease-causing mutations in prenatal diagnosis, this study was conducted to uncover the possible mutations in an Iranian couple with a deceased offspring clinically diagnosed as having organic acidemia. Moreover, to prevent the occurrence of the mutation in the next pregnancy, we took the advantage of pre-implantation genetic diagnosis (PGD), which resulted in a successful pregnancy.

Case presentation

The affected individual was a 15-month-old boy who passed away due to aspiration pneumonia. The child presented at the age of 3 months with lethargy, protracted vomiting, hypotonia, and decreased level of consciousness. To find the mutated gene, Next Generation Sequencing (NGS) was performed as carrier testing for the parents and the results revealed a novel (private) heterozygous missense mutation in MUT gene (c.1055A > G, p.Q352R). After performing PGD on three blastomeres, one was identified as being homozygous wild-type that was followed by successful pregnancy.

Conclusions

Our study identified a novel, deleterious, heterozygous missense mutation in MUT gene in a couple and helps to consider the genetic counselling and prenatal diagnosis more seriously for this family with clinical phenotypes of organic acidemia.

Clinical and molecular characterization of three patients with Hepatocerebral form of mitochondrial DNA depletion syndrome: a case series

Background

Mitochondrial DNA depletion syndromes (MDS) are clinically and phenotypically heterogeneous disorders resulting from nuclear gene mutations. The affected individuals represent a notable reduction in mitochondrial DNA (mtDNA) content, which leads to malfunction of the components of the respiratory chain. MDS is classified according to the type of affected tissue; the most common type is hepatocerebral form, which is attributed to mutations in nuclear genes such as DGUOK and MPV17. These two genes encode mitochondrial proteins and play major roles in mtDNA synthesis.

Case presentation

In this investigation patients in three families affected by hepatocerebral form of MDS who were initially diagnosed with tyrosinemia underwent full clinical evaluation. Furthermore, the causative mutations were identified using next generation sequencing and were subsequently validated using sanger sequencing. The effect of the mutations on the gene expression was also studied using real-time PCR. A pathogenic heterozygous frameshift deletion mutation in DGUOK gene was identified in parents of two affected patients (c.706–707 + 2 del: p.k236 fs) presenting with jaundice, impaired fetal growth, low-birth weight, and failure to thrive who died at the age of 3 and 6 months in family I. Moreover, a novel splice site mutation in MPV17 gene (c.461 + 1G > C) was identified in a patient with jaundice, muscle weakness, and failure to thrive who died due to hepatic failure at the age of 4 months. A 5-month-old infant presenting with jaundice, dark urine, poor sucking, and feeding problems was also identified to have another novel mutation in MPV17 gene leading to stop gain mutation (c.277C > T: p.(Gln93*)).

Conclusions

These patients had overlapping clinical features with tyrosinemia. MDS should be considered a differential diagnosis in patients presenting with signs and symptoms of tyrosinemia.

Prevalence and characterization of extended spectrum β-lactamases in Klebsiella-Enterobacter-Serratia group bacteria, in Algeria

OBJECTIVES

The authors had for aim to assess the local epidemiology, antibiotic resistance, and molecular typing of expanded spectrum betalactamase producing Klebsiella, Enterobacter, and Serratia (ESBL KES).

MATERIALS AND METHODS

Two hundred and seven strains of the KES group were isolated in the microbiology laboratory of the Annaba Ibn Rochd hospital in 2009. The antibiotic resistance (diffusion method and MIC) was tested and ESBL detection was performed as recommended by the Clinical Laboratory Standard Institute (CLSI). The characterization of genes for resistance to β-lactams (CTX-M-1, TEM, and SHV) and AmpC cephalosporinase (DHA-1) was performed by polymerase chain reaction. The epidemiological relationship among identified strains was analyzed by Pulsed Field Gel Electrophoresis (PFGE). Genetic transfers were performed by conjugation using sodium azide resistant Escherichia coli K(12)J(5) as recipient strain.

RESULTS

The overall incidence of ESBL KES was 31.4% (65/207) distributed as follows: 17.4% of Klebsiella spp., 7.2% Enterobacter spp., and 6.8% Serratia marcescens. The β-lactamase CTX-M 1 types were predominant (88%), followed by TEM (36.5%), and SHV (31.1%). Twenty-three strains expressed at least two bla genes. DHA-1 type cephalosporinase was found in 4 E. cloacae associated with CTX-M-1. Several epidemic clones were determined. Conjugation experiments showed that bla(CTX-M), bla(TEM), and bla(SHV) were carried by conjugative plasmids of high molecular weight (≥125kb).

CONCLUSIONS

This study revealed a high frequency of ESBL KES with a predominance of CTX-M-1. This high rate of ESBLs could be due to a clonal spread and the emergence of new epidemic clones.