Adult Carriers Research Articles

Adult Inactivation of the Recessive Polycystic Kidney Disease Gene Causes Polycystic Liver Disease.

A major difference between autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD) lies in the pattern of inheritance, and the resultant timing and focality of cyst formation. In both diseases, cysts form in the kidney and liver as a consequence of the cellular recessive genotype of the respective disease gene, but this occurs by germline inheritance in ARPKD and somatic second hit mutations to the one normal allele in ADPKD. The fibrocystic liver phenotype in ARPKD is attributed to abnormal ductal plate formation because of the absence of PKHD1 expression during embryogenesis and organ development. The finding of polycystic liver disease in a subset of adult PKHD1 heterozygous carriers raises the question of whether somatic second hit mutations in PKHD1 in adults may also result in bile duct-derived cyst formation. We used an adult-inducible Pkhd1 mouse model to examine whether Pkhd1 has a functional role in maintaining bile duct homeostasis after normal liver development. Inactivation of Pkhd1 beginning at 4 weeks of age resulted in a polycystic liver phenotype with minimal fibrosis at 17 weeks. Increased biliary epithelium, which lines these liver cysts, was most pronounced in female mice. We assessed genetic interaction of this phenotype with either reduced or increased copies of Pkd1, and found no significant effects on the Pkhd1 phenotype in the liver or kidney from altered Pkd1 expression. Somatic adult inactivation of Pkhd1 results in a polycystic liver phenotype. Pkhd1 is a required gene in adulthood for biliary structural homeostasis independent of Pkd1. This suggests that PKHD1 heterozygous carrier patients can develop liver cysts after somatic mutations in their normal copy of PKHD1.

Clinical phenotype of adult offspring carriers of the p.Pro392Leu mutation within the SQSTM1 gene in Paget's disease of bone

Paget's disease of bone (PDB) is a common chronic bone disorder. In the French-Canadian population, the p.Pro392Leu mutation within the SQSTM1 gene is involved in 46% of familial forms. In New Zealand, the emergence of PDB in offspring inheriting SQSTM1 mutations was reported to be delayed by a decade compared to their parents. We aimed at assessing the clinical phenotype of offspring carriers of this mutation in our French-Canadian cohort. We reviewed research records from adult offspring carriers of this mutation aged <90 years and their affected parents. In parents, we collected data on sex, age at diagnosis, number of affected bones, total serum alkaline phosphatase levels (tALPs) at diagnosis. In offspring, PDB extended phenotype assessment relying on tALPs, bone specific alkaline phosphatase levels (bALPs), procollagen type 1 amino-terminal propeptide (P1NP), whole body bone scan and skull and pelvis radiographs, was performed at inclusion from 1996 to 2009 and updated in 2016 to 2018, if not done during the past 8 years. The results showed that among the 36 offspring with an updated phenotype, four of them developed a clinical phenotype of PDB characterized by monostotic or polyostotic increased bone uptake associated with typical radiographic lesions in the affected sites, representing an incidence of 1.83 per 1000 person-years. Moreover, the age at PDB diagnosis was delayed by at least 10 years in the adult offspring carriers of the p.Pro392Leu mutation versus their affected parents. Our findings support the utility of a regular monitoring of the adult offspring without PDB but carriers of this mutation.

Computer versus cardiologist: Is a machine learning algorithm able to outperform an expert in diagnosing a phospholamban p.Arg14del mutation on the electrocardiogram?

Phospholamban (PLN) p.Arg14del mutation carriers are known to develop dilated and/or arrhythmogenic cardiomyopathy, and typical electrocardiographic (ECG) features have been identified for diagnosis. Machine learning is a powerful tool used in ECG analysis and has shown to outperform cardiologists. We aimed to develop machine learning and deep learning models to diagnose PLN p.Arg14del cardiomyopathy using ECGs and evaluate their accuracy compared to an expert cardiologist. We included 155 adult PLN mutation carriers and 155 age- and sex-matched control subjects. Twenty-one PLN mutation carriers (13.4%) were classified as symptomatic (symptoms of heart failure or malignant ventricular arrhythmias). The data set was split into training and testing sets using 4-fold cross-validation. Multiple models were developed to discriminate between PLN mutation carriers and control subjects. For comparison, expert cardiologists classified the same data set. The best performing models were validated using an external PLN p.Arg14del mutation carrier data set from Murcia, Spain (n = 50). We applied occlusion maps to visualize the most contributing ECG regions. In terms of specificity, expert cardiologists (0.99) outperformed all models (range 0.53-0.81). In terms of accuracy and sensitivity, experts (0.28 and 0.64) were outperformed by all models (sensitivity range 0.65-0.81). T-wave morphology was most important for classification of PLN p.Arg14del carriers. External validation showed comparable results, with the best model outperforming experts. This study shows that machine learning can outperform experienced cardiologists in the diagnosis of PLN p.Arg14del cardiomyopathy and suggests that the shape of the T wave is of added importance to this diagnosis.

Decrease in the prevalence of hepatitis B and D virus infections in an endemic area in Peru 23 years after the introduction of the first pilot vaccination program against hepatitis B.

In 1991, Peru launched the first vaccination program against hepatitis B in children aged under 5 years in the hyperendemic [hepatitis B virus (HBV) and hepatitis D virus (HDV)] province of Abancay. We conducted a cross-sectional study to determine the prevalence of HBV and HDV infections, 23 years after the launch of the vaccination program, as well as the post-vaccine response against hepatitis B in terms of prevalence of hepatitis B surface antibody (anti-HBs ≥10 mUI/ml). Among 3165 participants aged from 0 to 94 years, the prevalence rates of hepatitis B surface antigen (HBsAg), and hepatitis B core antibody (total anti-HBc) were 1.2% [95% confidence interval (CI) 0.85-1.64%], and 41.67% (95% CI 39.95-43.41%), respectively. The prevalence rate of anti-HBs at protective levels (≥10 mUI/ml) in individuals who HBsAg and anti-HBc negative was 66.36% (95% CI 64.15-68.51%). The prevalence rate of HBsAg in children aged <15 years was nil, and among adult HBsAg carriers, the prevalence of hepatitis D antibody (anti-HDV) was 5.26% (2/38; 95% CI 0.64-17.74). These findings showed that HBV prevalence has changed from high to low endemicity, 23 years following implementation of the vaccination program against hepatitis B, and HDV infection was not detected in those aged <30 years.

Penetrance of Hypertrophic Cardiomyopathy in Sarcomere Protein Mutation Carriers

BackgroundPredictive genetic screening of relatives of patients with hypertrophic cardiomyopathy (HCM) caused by sarcomere protein (SP) gene mutations is current standard of care, but there are few data on long-term outcomes in mutation carriers without HCM. ObjectivesThe aim of this study was to determine the incidence of new HCM diagnosis in SP mutation carriers. MethodsThis was a retrospective analysis of adult and pediatric SP mutation carriers identified during family screening who did not fulfill diagnostic criteria for HCM at first evaluation. ResultsThe authors evaluated 285 individuals from 156 families (median age 14.2 years [interquartile range: 6.8 to 31.6 years], 141 [49.5%] male individuals); 145 (50.9%) underwent cardiac magnetic resonance (CMR). Frequency of causal genes was as follows: MYBPC3 n = 123 (43.2%), MYH7 n = 69 (24.2%), TNNI3 n = 39 (13.7%), TNNT2 n = 34 (11.9%), TPM1 n = 9 (3.2%), MYL2 n = 6 (2.1%), ACTC1 n = 1 (0.4%), multiple mutations n = 4 (1.4%). Median follow-up was 8.0 years (interquartile range: 4.0 to 13.3 years) and 86 (30.2%) patients developed HCM; 16 of 50 (32.0%) fulfilled diagnostic criteria on CMR but not echocardiography. Estimated HCM penetrance at 15 years of follow-up was 46% (95% confidence interval [CI]: 38% to 54%). In a multivariable model adjusted for age and stratified for CMR, independent predictors of HCM development were male sex (hazard ratio [HR]: 2.91; 95% CI: 1.82 to 4.65) and abnormal electrocardiogram (ECG) (HR: 4.02; 95% CI: 2.51 to 6.44); TNNI3 variants had the lowest risk (HR: 0.19; 95% CI: 0.07 to 0.55, compared to MYBPC3). ConclusionsFollowing a first negative screening, approximately 50% of SP mutation carriers develop HCM over 15 years of follow-up. Male sex and an abnormal ECG are associated with a higher risk of developing HCM. Regular CMR should be considered in long-term screening.

Cancer surveillance and distress among adult pathogenic TP53 germline variant carriers in Germany: A multicenter feasibility and acceptance survey.

Li-Fraumeni syndrome (LFS) is a high-risk cancer predisposition syndrome caused by pathogenic germline variants of TP53. Cancer surveillance has noted a significant survival advantage in individuals with LFS; however, little is known about the feasibility, acceptance, and psychosocial effects of such a program. Pathogenic TP53 germline variant carriers completed a 7-part questionnaire evaluating sociodemographics, cancer history, surveillance participation, reasons for nonadherence, worries, and distress adapted from the Cancer Worry Scale. Counselees' common concerns and suggestions were assessed in MAXQDA Analytics Pro 12. Forty-nine participants (46 females and 3 males), aged 40.0 ± 12.6years, formed the study population; 43 (88%) had a personal cancer history (including multiple cancers in 10 [20%]). Forty-three individuals participated (88%) in surveillance during the study or formerly. Willingness to undergo surveillance was influenced by satisfaction with genetic testing and counseling (P=.019 [Fisher-Yates test]) but not by sociodemographics, cancer history, or distress level. Almost one-third of the participants reported logistical difficulties in implementing surveillance because of the high frequency of medical visits, scheduling difficulties, and the travel distance to their surveillance providers. Self-reported distress and perceived emotional burden for family members and partners were moderate (median for self-reported distress, 3.3; median for perceived emotional burden, 3.0). For both, the interquartile range was moderate to very high (2.7-3.7 and 3.0-3.7, respectively). Individuals with LFS require efficient counseling as well as an accessible, well-organized, interdisciplinary, standardized surveillance program to increase adherence and psychological coping.

Biological and clinical characteristics of gene carriers far from predicted onset in the Huntington's disease Young Adult Study (HD-YAS): a cross-sectional analysis.

SummaryBackgroundDisease-modifying treatments are in development for Huntington's disease; crucial to their success is to identify a timepoint in a patient's life when there is a measurable biomarker of early neurodegeneration while clinical function is still intact. We aimed to identify this timepoint in a novel cohort of young adult premanifest Huntington's disease gene carriers (preHD) far from predicted clinical symptom onset.MethodsWe did the Huntington's disease Young Adult Study (HD-YAS) in the UK. We recruited young adults with preHD and controls matched for age, education, and sex to ensure each group had at least 60 participants with imaging data, accounting for scan fails. Controls either had a family history of Huntington's disease but a negative genetic test, or no known family history of Huntington's disease. All participants underwent detailed neuropsychiatric and cognitive assessments, including tests from the Cambridge Neuropsychological Test Automated Battery and a battery assessing emotion, motivation, impulsivity and social cognition (EMOTICOM). Imaging (done for all participants without contraindications) included volumetric MRI, diffusion imaging, and multiparametric mapping. Biofluid markers of neuronal health were examined using blood and CSF collection. We did a cross-sectional analysis using general least-squares linear models to assess group differences and associations with age and CAG length, relating to predicted years to clinical onset. Results were corrected for multiple comparisons using the false discovery rate (FDR), with FDR <0·05 deemed a significant result.FindingsData were obtained between Aug 2, 2017, and April 25, 2019. We recruited 64 young adults with preHD and 67 controls. Mean ages of participants were 29·0 years (SD 5·6) and 29·1 years (5·7) in the preHD and control groups, respectively. We noted no significant evidence of cognitive or psychiatric impairment in preHD participants 23·6 years (SD 5·8) from predicted onset (FDR 0·22–0·87 for cognitive measures, 0·31–0·91 for neuropsychiatric measures). The preHD cohort had slightly smaller putamen volumes (FDR=0·03), but this did not appear to be closely related to predicted years to onset (FDR=0·54). There were no group differences in other brain imaging measures (FDR >0·16). CSF neurofilament light protein (NfL), plasma NfL, and CSF YKL-40 were elevated in this far-from-onset preHD cohort compared with controls (FDR<0·0001, =0·01, and =0·03, respectively). CSF NfL elevations were more likely in individuals closer to expected clinical onset (FDR <0·0001).InterpretationWe report normal brain function yet a rise in sensitive measures of neurodegeneration in a preHD cohort approximately 24 years from predicted clinical onset. CSF NfL appears to be a more sensitive measure than plasma NfL to monitor disease progression. This preHD cohort is one of the earliest yet studied, and our findings could be used to inform decisions about when to initiate a potential future intervention to delay or prevent further neurodegeneration while function is intact.FundingWellcome Trust, CHDI Foundation.

Faster Cortical Thinning and Surface Area Loss in Presymptomatic and Symptomatic C9orf72 Repeat Expansion Adult Carriers.

C9orf72 expansion is the most common genetic cause of frontotemporal dementia (FTD). We examined aging trajectories of cortical thickness (CTh) and surface area in C9orf72 expansion adult carriers compared to healthy controls to characterize preclinical cerebral changes leading to symptoms. Data were obtained from the Genetic Frontotemporal Dementia Initiative. T1-weighted magnetic resonance imaging scans were processed with CIVET 2.1 to extract vertex-wide CTh and cortical surface area (CSA). Symptomatic and presymptomatic subjects were compared to age-matched controls using mixed-effects models, controlling for demographic variables. Aging trajectories were compared between carriers and noncarriers by testing the "age by genetic status" interaction. False discovery rate corrections were applied to all vertex-wide analyses. The sample included 640 scans from 386 subjects, including 54 symptomatic C9orf72 carriers (72.2% behavioral variant FTD), 83 asymptomatic carriers, and 249 controls (age range = 18-86 years). Symptomatic carriers showed fairly symmetric reduction in CTh/CSA in most of the frontal lobes, in addition to large temporoparietal areas. Presymptomatic subjects had reduced CTh/CSA in more restricted areas of the medial frontoparietal lobes, in addition to scattered lateral frontal, parietal, and temporal areas. These differences were explained by faster cortical thinning linearly throughout adulthood in a similar anatomical distribution, with differences emerging in the early 30s. CSA reduction was also faster in mutation carriers predominantly in the ventrofrontal regions. C9orf72 mutation carriers have faster cortical thinning and surface loss throughout adulthood in regions that show atrophy in symptomatic subjects. This suggests that the pathogenic effects of the mutation lead to structural cerebral changes decades prior to symptoms. ANN NEUROL 2020 ANN NEUROL 2020;88:113-122.

Role of mitochondrial DNA variants in the development of fragile X-associated tremor/ataxia syndrome

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that appears in at least one-third of adult carriers of FMR1 premutation. Several studies have shown that mitochondrial dysfunction may play a role in neurodegenerative disorders. In order to assess whether mitochondrial DNA variants are involved in the risk of developing FXTAS we evaluated the frequency of mitochondrial haplogroups in 132 unrelated Spanish FMR1 premutation carriers. In addition, the entire mitogenome of 26 FMR1 premutation carriers was sequenced using massively parallel sequencing technologies to analyze mitochondrial DNA variants. Statistical analyses reveal a significant difference in the frequency of T haplogroup. Data analysis of mitochondrial DNA sequences evidence an association between FXTAS and the burden of heteroplasmic variants as well as their distribution. Our results suggest that haplogroup T might be a potential protective factor for FXTAS and that FXTAS individuals accumulate higher rates of heteroplasmic variants in compromised regions of the mitochondrial genome. These results may explain, in part, the role of mitochondrial DNA in the development of FXTAS.

Whole-body MRI within a surveillance program for carriers with clinically actionable germline TP53 variants - the Swedish constitutional TP53 study SWEP53

BackgroundThe current guidelines in Sweden regarding individuals with a clinically actionable (i.e. pathogenic or likely pathogenic) germline TP53 variant recommend patients to take part of the national Swedish P53 Study (SWEP53).MethodsThe study comprises a patient registry (mandatory for all participants) and three optional parts: a biobank, a surveillance program and a psychosocial evaluation of the surveillance. All known adult eligible carriers regardless of age are offered to take part of the surveillance program offering MRI yearly of the whole-body, breast, and brain as well as breast ultrasound. A special surveillance program is offered for individuals 15–18 years old with a 50% risk of being a mutation carrier or with a verified TP53 variation, includes ultrasound of the abdomen and urine corticosteroid profiles. Clinically motivated further examinations are performed upon need. The national inclusion is performed through the six clinical genetic units in Sweden at Umeå, Uppsala, Stockholm, Gothenburg, Linköping and Lund, and the surveillance is mainly performed through the oncology clinics.ResultsTo date, a total of 41 adults and 11 children have been included in the study.ConclusionsThe SWEP53 is the first structured national surveillance program including radiological and clinical routines for TP53 mutation carriers in the Scandinavian setting. The aim of this publication is to present and describe the ongoing Swedish surveillance study to encourage the initiation of similar studies and to contribute to the knowledge of adequate clinical handling of these cancer prone families.Trial registrationTrial registration number: ISRCTN13103571, retrospectively registered on 14/10/2019.

Seroepidemiological evidence for Taenia solium taeniasis/cysticercosis in three Venezuelan rural communities.

Taenia solium is the most common parasite infection of the brain, causing neurocysticercosis and typically found in rural communities with free-ranging pigs. Identification of transmission in rural areas is essential for its control. Risk factors and transmission of the parasite were evaluated in three rural Venezuelan communities (Valle del Rio and Potrero Largo, Cojedes state; and Palmarito, Portuguesa state) by a questionnaire (112 households) and coprological (492 samples) and serological (433 human and 230 porcine sera) analysis, respectively. Typical risk factors were found in all three communities: free-foraging pig husbandry, deficient sanitary conditions, high open defecation and ignorance of the parasite life cycle. Coprological examinations revealed a high level of soil-transmitted parasites. Importantly, two T. solium adult worm carriers were identified in each of the three communities. Anti-metacestode antibodies and the HP10 secreted metacestode glycoprotein were detected at significant levels in human and porcine sera in Valle del Rio, Potrero Largo and Palmarito. In conclusion, these communities may be considered to be endemic for taeniasis/cysticercosis, and the instigation of an appropriate control programme is recommended.

HTLV-1 proviral load in infective dermatitis associated with HTLV-1 does not increase after the development of HTLV-1-associated myelopathy/tropical spastic paraparesis and does not decrease after IDH remission.

IntroductionInfective dermatitis associated with HTLV-1 (IDH) is a recurrent eczema which affects children vertically infected with HTLV-1. In Bahia, Brazil, we recently reported that 47% of IDH patients also develop juvenile HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a progressive disabling disorder which is typically reported in adult HTLV-1 carriers. IDH may also predispose to adult T-cell leukemia/lymphoma, a neoplasm associated with HTLV-1. The factors relating to the development of HTLV-1-associated juvenile diseases have not yet been defined. HTLV-1 proviral load (PVL) is one of the main parameters related to the development of HTLV-1 associated diseases in adults. In the current study, we investigated the role of PVL in IDH and juvenile HAM/TSP.Methodology/Principal findingsThis is a cohort study that included fifty-nine HTLV-1 infected children and adolescents, comprising 16 asymptomatic carriers, 18 IDH patients, 20 patients with IDH and HAM/TSP (IDH/HAM/TSP) and five with HAM/TSP. These patients were followed-up for up to 14 years (median of 8 years). We found that PVL in IDH and IDH/HAM/TSP patients were similarly higher than PVL in juvenile asymptomatic carriers (p<0.0001). In those IDH patients who developed HAM/TSP during follow-up, PVL levels did not vary significantly. HAM/TSP development did not occur in those IDH patients who presented high levels of PVL. IDH remission was associated with an increase of PVL. Inter-individual differences in PVL were observed within all groups. However, intra-individual PVL did not fluctuate significantly during follow-up.Conclusions/SignificanceHigh PVL in IDH patients was not necessary indicative of progression to HAM/TSP. PVL did not decrease after IDH remission. The maintenance of high PVL after remission could favor early development of ATL. Therefore, IDH patients would have to be followed-up even after remission of IDH and for a long period of time.

Unsatisfying antiviral therapeutic effect in patients with mother-to-child transmissed chronic hepatitis B virus infection

Background:Few data are available regarding the progression of liver disease and therapeutic efficacy in chronic hepatitis B virus (HBV) carriers infected by mother-to-child transmission (MTCT). This study aimed to investigate these two aspects by comparing the adult chronic HBV carriers in MTCT group with those in horizontal transmission group.Methods:The 683 adult chronic HBV patients qualified for liver biopsy including 191 with MTCT and 492 with horizontal transmission entered the multi-center prospective study from October 2013 to May 2016. Biopsy results from 217 patients at baseline and 78 weeks post antiviral therapy were collected.Results:Patients infected by MTCT were more likely to have e antigen positive (68.6% vs. 58.2%, χ2 = –2.491, P = 0.012) than those with horizontal transmission. However, in patients with MTCT, levels of alkaline phosphatase (ALP) (P = 0.031), Fibroscan (P = 0.013), N-terminal propeptide of Type III procollagen (PIIINP) (P = 0.014), and Laminin (LN) (P = 0.006) were high, in contrast to the patients with horizontal transmission for whom the levels of albumin (ALB) (P = 0.041), matrix metalloproteinase-3 (MMP-3) (P = 0.001) were high. The 47.2% of patients with MTCT and 36.8% of those with horizontal transmission had significant liver fibrosis (P = 0.013). Following antiviral therapy for 78 weeks, 21.2% and 38.0% patients with MTCT and horizontal transmission acquired hepatitis B e antigen (HBeAg) clearance, respectively (P = 0.043), and the virological response rates were 54.7% and 74.1% in the MTCT and horizontal groups, respectively (P = 0.005). MTCT was a risk factor for HBeAg clearance and virological response.Conclusion:Adult patients with MTCT were more prone to severe liver diseases, and the therapeutic efficacy was relatively poor, which underlined the importance of earlier, long-term treatment and interrupting perinatal transmission.Trial Registration:NCT01962155; https://clinicaltrials.gov.

Psychosocial effects of whole-body MRI screening in adult high-risk pathogenic TP53 mutation carriers: a case-controlled study (SIGNIFY)

BackgroundGermline TP53 gene pathogenic variants (pv) cause a very high lifetime risk of developing cancer, almost 100% for women and 75% for men. In the UK, annual MRI breast screening...

P.320Cardiac phenotypic expressions in female carriers of a canine model of Duchenne muscular dystrophy

Golden Retriever muscular dystrophy (GRMD) represents an animal model that recapitulates human Duchenne muscular dystrophy (DMD) and provides a unique tool to investigate the pathogenic mechanisms and clues to understand the disease process. The primary presenting symptom in most dystrophinopathies is skeletal muscle weakness. However, cardiac muscle is similarly affected in DMD. Human female carriers of DMD, although frequently asymptomatic, can develop cardiac abnormalities. Our primary goal was to use female GRMD carriers as a test model for this subset of patients and establish a comprehensive reference dataset on a population of young adult GRMD carriers (N=19, 2 to 8 years) compared to healthy controls (N=8). Methodological approach was based on structural and functional evaluations, involving cardiac MRI as well as ECG Holter monitoring. Necropsy data should be correlated to the in vivo observations. In the context of cardiomyopathies, alterations of the cardiac rhythm as well as modifications of the cardiac interstitium like fibrosis, usually precede the appearance of overt systolic dysfunction. Preliminary results reveal quantifiable abnormalities in myocardial structure, contractile function or cardiac rhythm in all female carriers. Whereas, global ejection fractions were preserved, alterations of segmental contractility were observed. The longitudinal relaxation time constant (T1) of the myocardium was altered and might be due to increased water content or other changes of the local molecular environment related to fibrosis. All the carrier females presented with severe ventricular arrhythmias grading from 3a (polymorphism) to 4b (salvos) in the Lown classification. Some animals also presented with supraventricular arrhythmias. At necropsy, all female carriers had obvious myocardial fibrosis. Thus, female GRMD carriers appear as a valuable animal model to explore further the pathophysiology of the subset of female patients carrying a dystrophin mutation.

NaV1.2 haploinsufficiency in Scn2a knock-out mice causes an autistic-like phenotype attenuated with age

Mutations of the SCN2A gene, encoding the voltage gated sodium channel NaV1.2, have been associated to a wide spectrum of epileptic disorders ranging from benign familial neonatal-infantile seizures to early onset epileptic encephalopathies such as Ohtahara syndrome. These phenotypes may be caused by either gain-of-function or loss-of-function mutations. More recently, loss-of-function SCN2A mutations have also been identified in patients with autism spectrum disorder (ASD) without overt epileptic phenotypes. Heterozygous Scn2a knock-out mice (Scn2a+/−) may be a model of this phenotype. Because ASD develops in childhood, we performed a detailed behavioral characterization of Scn2a+/− mice comparing the juvenile/adolescent period of development and adulthood. We used tasks relevant to ASD and the different comorbidities frequently found in this disorder, such as anxiety or intellectual disability. Our data demonstrate that young Scn2a+/− mice display autistic-like phenotype associated to impaired memory and reduced reactivity to stressful stimuli. Interestingly, these dysfunctions are attenuated with age since adult mice show only communicative deficits. Considering the clinical data available on patients with loss-of-function SCN2A mutations, our results indicate that Scn2a+/− mice constitute an ASD model with construct and face validity during the juvenile/adolescent period of development. However, more information about the clinical features of adult carriers of SCN2A mutations is needed to evaluate comparatively the phenotype of adult Scn2a+/− mice.

APOE modifies the interaction of entorhinal cerebral blood flow and cortical thickness on memory function in cognitively normal older adults

ObjectiveThe ε4 allele of the apolipoprotein E (APOE) gene increases risk for cognitive decline in normal and pathologic aging. However, precisely how APOE ε4 exerts its negative impact on cognition is poorly understood. The present study aimed to determine whether APOE genotype (ε4+ vs. ε4-) modifies the interaction of medial temporal lobe (MTL) resting cerebral blood flow (CBF) and brain structure (cortical thickness [CT], volume [Vo]) on verbal memory performance. MethodsMultiple linear regression models were employed to investigate relationships between APOE genotype, arterial spin labeling MRI-measured CBF and FreeSurfer-based CT and Vo in four MTL regions of interest (left and right entorhinal cortex and hippocampus), and verbal memory performance among a sample of 117 cognitively normal older adults (41 ε4+, 76 ε4-) between the ages of 64 and 89 (mean age ​= ​73). ResultsResults indicated that APOE genotype modified the interaction of CBF and CT on memory in the left entorhinal cortex, such that the relationship between entorhinal CBF and memory was negative (lower CBF was associated with better memory) in non-carriers with higher entorhinal CT, positive (higher CBF was associated with better memory) in non-carriers with lower entorhinal CT, and negative (higher CBF was associated with worse memory) in ε4 carriers with lower entorhinal CT. ConclusionsFindings suggest that older adult APOE ε4 carriers may experience vascular dysregulation and concomitant morphological alterations in the MTL that interact to negatively affect memory even in the absence overt clinical symptoms, providing potential insight into the mechanistic link between APOE ε4 and detriments in cognition. Moreover, findings suggest a distinct multimodal neural signature in ε4 carriers (higher CBF and lower CT in the entorhinal cortex) that could aid in the identification of candidates for future clinical trials aimed at preventing or slowing cognitive decline. Differential findings with respect to ε4 carriers and non-carriers are discussed in the context of neurovascular compensation.

Novel dominant KATP channel mutations in infants with congenital hyperinsulinism: Validation by in vitro expression studies and in vivo carrier phenotyping.

Inactivating mutations in the genes encoding the two subunits of the pancreatic beta‐cell KATP channel, ABCC8 and KCNJ11, are the most common finding in children with congenital hyperinsulinism (HI). Interpreting novel missense variants in these genes is problematic, because they can be either dominant or recessive mutations, benign polymorphisms, or diabetes mutations. This report describes six novel missense variants in ABCC8 and KCNJ11 that were identified in 11 probands with congenital HI. One of the three ABCC8 mutations (p.Ala1458Thr) and all three KCNJ11 mutations were associated with responsiveness to diazoxide. Sixteen family members carried the ABCC8 or KCNJ11 mutations; only two had hypoglycemia detected at birth and four others reported symptoms of hypoglycemia. Phenotype testing of seven adult mutation carriers revealed abnormal protein‐induced hypoglycemia in all; fasting hypoketotic hypoglycemia was demonstrated in four of the seven. All of six mutations were confirmed to cause dominant pathogenic defects based on in vitro expression studies in COSm6 cells demonstrating normal trafficking, but reduced responses to MgADP and diazoxide. These results indicate a combination of in vitro and in vivo phenotype tests can be used to differentiate dominant from recessive KATP channel HI mutations and personalize management of children with congenital HI.

Intracellular FMRpolyG-Hsp70 complex in fibroblast cells from a patient affected by fragile X tremor ataxia syndrome

BackgroundFragile X-associated tremor/ataxia syndrome is a late-onset neurodegenerative disorder that affects about 40% of carriers of CGG-repeat expansions in the premutation range within the fragile X gene (FMR1). Main clinical features include intention tremor, cerebellar ataxia, and parkinsonism. Recently, great emphasis on the deposition of soluble aggregates produced by a RAN translation process, as main pathogenic mechanism, has been given. These aggregates contain a small protein with a polyglycine stretch on the aminoterminal end named FMRpolyG and, so far, have been isolated and characterized in drosophila and mouse models, in post mortem brain of fragile X-associated tremor/ataxia syndrome patients, in fibroblasts of fragile primary ovarian insufficiency patients, but never in fibroblasts from a fragile X-associated tremor/ataxia living patients. In adult carriers the syndrome is frequently misdiagnosed due to the lack of specific markers. MethodsWe standardized immunocytochemistry, immunoprecipitation and western blot procedures to study and biochemically characterize the FMRpolyG protein in fibroblasts from human skin biopsy. ResultsWe demonstrate for the first time, in fibroblasts from a patient affected by Fragile X-associated tremor/ataxia syndrome, the presence ex vivo of inclusions consisting of FMRpolyG- Hsp70 soluble aggregates. ConclusionThese observations can pave the way to develop a cellular model for studying ex vivo and in vitro the mechanisms involved in the production of FMRpolyG aggregates, their toxicity, and the role of the FMRpolyG-Hsp70 interaction in the pathogenesis of fragile X-associated tremor/ataxia syndrome.

Fragile X-associated tremor/ataxia syndrome: Regional decrease of mitochondrial DNA copy number relates to clinical manifestations.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that appears in at least one-third of adult carriers of a premutation (55-200 CGG repeats) in the fragile X mental retardation 1 (FMR1) gene. Several studies have shown that mitochondrial dysfunction may play a central role in aging and also in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease as well as in FXTAS. It has been recently proposed that mtDNA copy number, measured by the number of mitochondrial genomes per nuclear genome (diploid), could be a useful biomarker of mitochondrial dysfunction. In order to elucidate the role of mtDNA variation in the pathogenesis of FXTAS, mtDNA copy number was quantified by digital droplet Polymerase chain reaction. In human brain samples, mtDNA levels were measured in the cerebellar vermis, dentate nucleus, parietal and temporal cortex, thalamus, caudate nucleus and hippocampus from a female FXTAS patient, a FMR1 premutation male carrier without FXTAS and from three male controls. The mtDNA copy number was further analyzed using this technology in dermal fibroblasts primary cultures derived from three FXTAS patients and three controls as well as in cortex and cerebellum of a CGG knock in FXTAS mice model. Finally, qPCR was carried out in human blood samples. Results indicate reduced mtDNA copy number in the specific brain region associated with disease progression in FXTAS patients, providing new insights into the role of mitochondrial dysfunction in the pathogenesis of FXTAS.