Autosomal-Recessive Intellectual Disability with Cerebellar Atrophy Syndrome Caused by Mutation of the Manganese and Zinc Transporter Gene SLC39A8.

Manganese (Mn) and zinc (Zn) are essential divalent cations used by cells as protein cofactors; various human studies and animal models have demonstrated the importance of Mn and Zn for development. Here we describe an autosomal-recessive disorder in six individuals from the Hutterite community and in an unrelated Egyptian sibpair; the disorder is characterized by intellectual disability, developmental delay, hypotonia, strabismus, cerebellar atrophy, and variable short stature. Exome sequencing in one affected Hutterite individual and the Egyptian family identified the same homozygous variant, c.112G>C (p.Gly38Arg), affecting a conserved residue of SLC39A8. The affected Hutterite and Egyptian individuals did not share an extended common haplotype, suggesting that the mutation arose independently. SLC39A8 is a member of the solute carrier gene family known to import Mn, Zn, and other divalent cations across the plasma membrane. Evaluation of these two metal ions in the affected individuals revealed variably low levels of Mn and Zn in blood and elevated levels in urine, indicating renal wasting. Our findings identify a human Mn and Zn transporter deficiency syndrome linked to SLC39A8, providing insight into the roles of Mn and Zn homeostasis in human health and development.

HFE H63D, C282Y and AGTR1 A1166C polymorphisms and brain white matter lesions in the aging brain.

Incidental white matter lesions (WML) are a common neuroradiological finding in elderly people and have been linked to dementia and depression. Various mechanisms including hypoxia and increased production of reactive oxygen species (ROS) are implicated in the etiology of WML. The hemochromatosis (HFE) gene p.H63D and p.C282Y polymorphisms have been linked to dysregulation of iron metabolism and increased levels of ROS, whereas Angiotensin II receptor 1 (AGTR1) c.1166A → C polymorphism is known as a vascular risk factor. These genetic polymorphisms were characterized in brains donated to the UK MRC Cognitive Function and Ageing Study (CFAS) to assess their potential role in the risk for development of age-related WML. The study cohort comprised 258 brain donated to CFAS. WML severity was assessed in the postmortem brain donations using magnetic resonance imaging (MRI) scans and scored using the Scheltens' scale. Polymerase chain reaction (PCR) amplification of extracted DNA followed by restriction enzyme digestion was used to genotype the samples. Genotypes were validated using direct sequencing in a smaller sample. The results show that HFE p.H63D polymorphism is not associated with WML severity in the whole cohort. However, there is a significant association of the D allele with severity of WML in noncarriers of the APOE ε4 allele. No association is demonstrated between the HFE p.C282Y nor the AGTR1 c.1166A → C polymorphisms and WML severity. The HFE gene appears to be a genetic risk factor for severe aging WML independently of the APOE ε4 genotype. This would support the role of iron-related oxidative stress, in addition to previously studied factors, e.g., hypoxia as potential risk factors for developing prominent aging WML.

The role of zinc supplementation on the metallothionein system in children with autism spectrum disorder.

The present research was carried out to elucidate the role of zinc (Zn) supplementation on the plasma concentration and gene expression, as well as the effects on cognitive-motor performance, in a cohort of children with autism spectrum disorder (ASD). The study was performed on a cohort of 30 pediatric subjects with ASD, encompassing an age range of 3-8 years. The impact of Zn supplementation was investigated in 3 months (or 12 weeks) on the ASD children. Each daily dosage of Zn was calculated as being equal to the body weight in kg plus 15-20 mg. The effect of Zn was also evaluated on the serum level of metallothionein 1 (MT-1A), and the severity of autism via scores on the Childhood Autism Rating Scale. The effect of Zn was investigated on the gene expression of MT1-A before and after Zn supplementation. The data of the present study showed an increase in cognitive-motor performance and an increased serum metallothionein concentration, as well as a significant lowering in the circulating serum levels of copper (Cu) following Zn supplementation. In the cohort of ASD patients, the genetic expression of MT-1 was higher after Zn therapy than before the treatment. In conclusion, Zn supplementation might be an important factor in the treatment of children with ASD.

A study of blood serotonin and serotonin transporter promoter variant (5-HTTLPR) polymorphism in Egyptian autistic children.

BACKGROUND: Autism spectrum disorder (ASD) is a complex, heterogeneous neurodevelopmental disorder with onset during early childhood. Most studies have reported an elevation in platelet serotonin in persons with autism. The serotonin (5-hydroxytryptamine; 5-HT) transporter in the brain uptakes 5-HT from extracellular spaces. It is also present in platelets, where it takes up 5-HT from plasma. Polymorphisms in serotonin transporter gene (SLC6A4) were frequently studied in many neuropsychiatric disorders. MATERIALS AND METHODS: We have measured the plasma 5-HT levels in 20 autistic male children and 20 control male children by the enzyme-linked immunosorbent assay (ELISA) method. In addition, the SLC6A4 promoter region (5-HTTLPR) insertion/deletion (I/D) polymorphism was studied, using whole genomic DNA. RESULTS: Plasma serotonin was significantly low in autistic children compared to control (P = 0.001), although correlation to severity of autism was not significant. The frequency of short (S) allele in autism cases was 10% and in the control group it was absent. CONCLUSION: Our study demonstrated an increased prevalence of 5-HTTLPR S allele in autism subjects. Significantly decreased plasma serotonin was detected in autism subjects, with no significant relationship between 5-HTTLPR genotype and plasma 5-HT being evident.

HFE gene polymorphisms and the risk for autism in Egyptian children and impact on the effect of oxidative stress.

BACKGROUND: Autism is among the commonest neurodevelopmental childhood disorders worldwide; its aetiology is still unknown. Iron metabolism alteration in the central nervous system is recently implicated as a risk factor for several neurodegenerative disorders. Haemochromatosis HFE gene polymorphisms (p.H63D and p.C282Y) have shown significant association with several neurological diseases. Some evidences show altered iron related proteins in serum of autistic children. The aim of this work is to conduct a preliminary pilot study for the association of HFE polymorphisms and autism. METHODS: All cases were referred from the clinic of special needs, National Research Centre, Cairo. Clinical diagnosis was based on the criteria for autistic disorder as defined in the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition, Text Revision (DSM-IV-TR). Whole genome DNA was extracted; p.H63D and p.C282Y genotyping was studied using specific sequence amplification followed by restriction enzyme digestion on a sample of autism patients (25 cases) and twenty controls. RESULTS: The p.H63D is more abundant than the C282Y among both autism and control samples. No significant association of p.H63D nor p.C282Y polymorphism and autism was revealed. CONCLUSION: We here report on the first pilot study of the possible genetic association between autism and HFE gene polymorphisms among Egyptians. Although our results do not prove the role of HFE polymorphisms as risk factors for autism, yet this does not exclude the role of iron in this prevalent disorder. Further extended studies are recommended to include other iron metabolism genes.

Brain iron dysregulation and the risk of ageing white matter lesions.

White matter lesions (WML) or leukoaraiosis is a major feature in cerebral imaging of older people, and their prevalence increases with age. The clinical effects of WML vary with the main impairment being detected in the cognitive functions, increased risk of severe depression and motor impairment. Although vascular comorbidities have been found to be the main changes in these brains, increased production of reactive oxygen species (ROS) could represent a risk factor for these lesions with elemental iron being a potential factor for ROS production. This study focuses on changes in iron, iron-regulating proteins and RNA expression of iron metabolism genes. Three groups of samples were used: WML, normal areas from lesional WM [NAWM (L)] as disease control and normal WM from control brains [NAWM(C)]. Ferric iron staining was undertaken using known Perl's reaction. Immunohistochemistry (IHC) of white matter for ceruloplasmin (Cp), haemochromatosis (HFE) and transferrin receptor (TfR) was done. Cellular localization of HFE and Cp was performed using dual-antibody IHC. Whole-genome RNA was extracted from WML, NAWM (L) and NAWM(C), and QPCR for HFE, TF, TfR, ceruloplasmin, ferritin and ferroportin was performed. Ferric iron staining shows increased diffuse iron staining among WML, followed by NAWM (L) and the least group being NAWM(C). IHC shows increased HFE and CP expression in lesional WM, while TfR shows no changes among the groups. HFE colocalized with vascular endothelium and microglia in WML and control samples, while Cp colocalized with microglia and some expression was shown by astrocytes. The mRNA expression using QPCR suggests a pattern that favours decreased intracellular iron influx, increased ferrous oxidation and increased iron export from the cells. Iron metabolism seems to be changed in brains with WML, increased elemental iron in these brains and in turn increased production of free oxidative radicals could represent a potentiating factor for the development of ageing WML.