The first genome-wide association study in the Argentinian and Chilean populations identifies shared genetics with Europeans in Alzheimer's disease.

INTRODUCTION: Genome-wide association studies (GWAS) are fundamental for identifying loci associated with diseases. However, they require replication in other ethnicities. METHODS: We performed GWAS on sporadic Alzheimer's disease (AD) including 539 patients and 854 controls from Argentina and Chile. We combined our results with those from the European Alzheimer and Dementia Biobank (EADB) in a meta-analysis and tested their genetic risk score (GRS) performance in this admixed population. RESULTS: We detected apolipoprotein E ε4 as the single genome-wide significant signal (odds ratio  = 2.93 [2.37-3.63], P = 2.6 × 10-23 ). The meta-analysis with EADB summary statistics revealed four new loci reaching GWAS significance. Functional annotations of these loci implicated endosome/lysosomal function. Finally, the AD-GRS presented a similar performance in these populations, despite the score diminished when the Native American ancestry rose. DISCUSSION: We report the first GWAS on AD in a population from South America. It shows shared genetics modulating AD risk between the European and these admixed populations. HIGHLIGHTS: This is the first genome-wide association study on Alzheimer's disease (AD) in a population sample from Argentina and Chile. Trans-ethnic meta-analysis reveals four new loci involving lysosomal function in AD. This is the first independent replication for TREM2L, IGH-gene-cluster, and ADAM17 loci. A genetic risk score (GRS) developed in Europeans performed well in this population. The higher the Native American ancestry the lower the GRS values.

[Nevoid basal cell carcinoma syndrome with corpus callosum agenesis, PTCH1 mutation and absence of basal cell carcinoma]. / Síndrome de carcinoma basocelular nevoide con agenesia de cuerpo calloso, mutación en PTCH1 y ausencia de carcinoma basocelular.

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) or Gorlin-Goltz syndrome is a rare autosomal dominant disorder, mainly due to PTCH1 gene mutations, that comprises a broad spectrum of clinical manifestations. The presence of multiple basal cell carcinomas (BCCs) is a cardinal sign in NBCCS, therefore cases in which BCCs are absent entails a delay in the diagnosis.We present a 14 years old boy with a clinical diagnosis of NBCCS by the presence of odontogenic cysts, hypertelorism, macrocephaly, and corpus callosum agenesia, but with absence of skin lesions. His 43 years old mother has NBCCS diagnosis and no history of BCCs. For a deeper study, PTCH1 mutation screening from peripheral blood samples were performed by both bidirectional sequencing and multiplex ligation dependent probe amplification (MLPA) techniques. The proband and his mother carry 25 pb duplication in exon 10 (c.1375dupl25bp) that causes a reading frameshift with a premature stop codon. Bioinformatics analysis predicted that this mutation results in a truncated protein shorter than normal. Our results suggest that complete clinical and genealogical studies accompanied by genetic analysis are essential in the early detection of the NBCCS cases such the one presented here.

Memory reconsolidation as a tool to endure encoding deficits in elderly.

Normal aging involves changes in the ability to acquire, consolidate and recall new information. It has been recently proposed that the reconsolidation process is also affected in older adults. Reconsolidation is triggered after reminder presentation, allowing memories to be modified: they can be impaired, strengthened or changed in their content. In young adults it was previously shown that the presentation of repetitive reminders induces memory strengthening one day after reactivation and the presentation of at least one reminder increases memory persistence several days after reactivation. However, until now this process has remained elusive in older adults. We hypothesize that older adults need a stronger reminder to induce memory strengthening through the reconsolidation process than young adults. To test this, we perform a three-day experiment. On day 1, participants learned 15 sound-word associations, on day 2 they received no reminders (NR group), one reminder (R group) or two rounds of reactivations (Rx2 group). Finally, they were tested on day 7. We found that, contrary to our hypothesis, older adults show a memory improvement triggered by repeated labilization/reconsolidation processes to an equal extent than young adults. These results open new perspectives into the use of reconsolidation to improve daily acquired information and the development of therapeutic home used tools to produce memory enhancement in healthy older adults or those with cognitive decline.

Nevoid Basal Cell Carcinoma Syndrome: PTCH1 Mutation Profile and Expression of Genes Involved in the Hedgehog Pathway in Argentinian Patients.

Nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple basal cell carcinomas (BCC), mainly caused by PTCH1 gene mutations. Our current study aimed to establish (1) PTCH1 germinal and somatic mutational status, (2) component and Hedgehog (HH) pathway targets gene expression patterns, and (3) profile variations according to the genetic background in BCC and normal surrounding skin (NSS). We collected 23 blood and 20 BCC patient samples and analyzed the PTCH1 gene using bidirectional sequencing and multiplex ligation-dependent probe amplification. Quantitative PCR was used to determine the mRNA expression levels of PTCH1, SMO, GLI3, and CCND1 in paired samples of BCC and NSS from 20 patients and four non-NBCCS skin controls (C). Our analyses identified 12 germline and five somatic sequence variants in PTCH1. mRNA levels of PTCH1, SMO, and GLI3 were higher in NSS compared to C samples, reaching maximum values in BCC samples (p < 0.05). NSS with PTCH1 germline mutations had modified SMO,PTCH1, and GLI3 mRNA levels compared to samples without mutation (p < 0.01). Two PTCH1 mutations in BCC led to an increase in PTCH1, SMO, and GLI3, and a decrease in CCND1 mRNA levels (p < 0.01 vs. BCC with germline mutation only). These results indicate that besides PTCH1, other genes are responsible for NBCCS and BCC development in a population exposed to high UV radiation. Additionally, the mutational events caused increased expression of HH-related genes, even in phenotypically normal skin.

Transethnic meta-analysis of rare coding variants in PLCG2, ABI3, and TREM2 supports their general contribution to Alzheimer's disease.

Rare coding variants in TREM2, PLCG2, and ABI3 were recently associated with the susceptibility to Alzheimer's disease (AD) in Caucasians. Frequencies and AD-associated effects of variants differ across ethnicities. To start filling the gap on AD genetics in South America and assess the impact of these variants across ethnicity, we studied these variants in Argentinian population in association with ancestry. TREM2 (rs143332484 and rs75932628), PLCG2 (rs72824905), and ABI3 (rs616338) were genotyped in 419 AD cases and 486 controls. Meta-analysis with European population was performed. Ancestry was estimated from genome-wide genotyping results. All variants show similar frequencies and odds ratios to those previously reported. Their association with AD reach statistical significance by meta-analysis. Although the Argentinian population is an admixture, variant carriers presented mainly Caucasian ancestry. Rare coding variants in TREM2, PLCG2, and ABI3 also modulate susceptibility to AD in populations from Argentina, and they may have a European heritage.

Co-Inheritance of Autosomal Dominant Polycystic Kidney Disease and Naevoid Basal Cell Carcinoma Syndrome: Effects on Renal Progression.

The calcium signalling and hedgehog (HH) signalling pathways operate in the primary cilium. Abnormalities in these pathways cause autosomal dominant polycystic kidney disease (ADPKD) and naevoid basal cell carcinoma syndrome (NBCCS) respectively. Several reports have proposed that hyperactivation of the HH pathway in animal models of polycystic kidney disease affects normal renal development and renal cyst phenotype. A family with 2 cases (a proband and her sister) of ADPKD and NBCCS coinheritance led us to investigate whether interactions may be present in the 2 pathways. The effect of HH pathway hyperactivation (due to c.573C>G mutation on PTCH1 gene that cause NBCCS) on renal ADPKD progression in the proband was compared to 18 age- and sex-matched ADPKD patients in a 9-year, prospective, follow-up study. Blood pressure, total kidney volume, estimated glomerular filtration rate, plasma copeptin, urine excretion of albumin, total protein and monocyte chemoattractant protein-1 (MCP-1) were analysed. Data for the sibling was not available. In the ADPKD group, blood pressure and estimated glomerular filtration rate were within normal values, and total kidney volume and MCP-1 increased (p < 0.01) throughout the study. In comparison, during the 9-year follow-up, the proband showed persistent hypertension (from 125/85 to 140/95 mm Hg), low total kidney volume (75 and 61% of median ADPKD), and a ninefold increase in urine MCP-1. We found no differences in urine excretion of albumin or plasma copeptin values. These results suggest that HH hyperactivation may play a minimal role in ADPKD progression. These observations can help to clarify the clinical impact of affected pathways in renal development and cystogenesis in humans.

Identification of PSEN2 mutation p.N141I in Argentine pedigrees with early-onset familial Alzheimer's disease.

Presenilin 2 gene (PSEN2) mutations account for <5% of all early-onset familial Alzheimer's disease (EOFAD) cases and only 13 have strong evidence for pathogenicity. We aimed to investigate the presence of PSEN2 mutation p.N141I and characterize the clinical phenotypes in 2 Argentine pedigrees (AR2 and AR3) with clinical symptoms of EOFAD. Detailed clinical assessments and genetic screening for PSEN2 and APOE genes were carried out in 19 individuals of AR2 and AR3 families. The p.N141I mutation was identified in all affected subjects and was associated with prominent early onset, rapidly progressive dementia, neurologic, and behavioral symptoms. AR2 and AR3 families share the same Volga German ancestry as all the families reported presenting this mutation. To our knowledge, this is the first report of PSEN2 mutation p.N141I in Argentina and even more, in South America. Our contribution increases the total number of described families carrying this mutation and help to improve the characterization of clinical phenotype in EOFAD associated to PSEN2 mutations.

[Progression of autosomic dominant polycystic kidney disease. Influence of endothelial NO synthase (ecNOS) and renin angiotensin system gene polymorphisms]. / Progresión de la poliquistosis renal autosómica dominante. Influencia de polimorfismos de genes de sintasa endotelial del óxido nítrico (ecNOS) y del sistema renina-angiotensina.

Glomerular filtration rate decline (GFRd) is variable in autosomic dominant polycystic kidney disease (ADPKD). In 88 ADPKD patients, GFRd was assessed by 1/S(Cr) and compared with the association to AT1A1166C (AT1R), AGTM235T (angiotensinogen) and ecNOSGlu298Asp (NO endothelial synthase) polymorphisms. Age at S(Cr) values of 2 and 6 mg/dl were assumed as beginning of progressive phase (A2) and end-stage-renal disease (A6), respectively. Polymorphisms were studied by PCR-RFLP. The group as a whole showed GFRd (ml/min/year) of 6.9+/-0.5; A2 and A6 of 48.9+/-1.3 and 55.0+/-1.4 years and mean arterial pressure of 111.2+/-1.2 mmHg. When A6 was considered, two populations were defined (< or = and > 55 years). In < or = 55 (assumed as PKD1 phenotype) (n=42), A2 and A6 of the AT1 1166CC genotype were 36.0+/-1.2 and 41.4+/-0.9 years vs AA-AC (42.8+/-1.0 and 47.5+/-0.8, p<0.001). A2 and A6 of the ecNOS298Asp/Asp genotype were 34.8+/-1.5 and 41.1+/-0.6 years vs. Glu/Glu-Glu/Asp (42.4+/-0.9 and 47.1+/-0.8, p<0.02). In AGT235TT genotype, GFRd was 12.4+/-2.2 ml/min/year vs MM-MT (7.9+/-0.7, p<0.03). This difference was also observed when all ADPKD patients were considered (TT: 11.02+/-1.5 vs. MM-MT: 6.44+/-0.5 ml/ min/year, p<0.003). AT1 1166CC and ecNOS 298Asp/Asp are associated with earlier A2 and A6 whereas AGT 235TT induce twofold increase in GFRd, suggesting that RAS and ecNOS are involved in ADPKD progression.

Síndrome de carcinoma basocelular nevoide con agenesia de cuerpo calloso, mutación en PTCH1 y ausencia de carcinoma basocelular

El síndrome del carcinoma basocelular nevoide (SCBCN) o de Gorlin-Goltz es un raro desorden autosómico dominante con un amplio espectro de manifestaciones clínicas. El signo cardinal es la presencia de múltiples carcinomas basocelulares (CBCs) y su ausencia demora el diagnóstico. Presentamos un adolescente de 14 años con diagnóstico de SCBCN por la presencia de queratoquistes odontogénicos, hiper­telorismo, macrocefalia y agenesia del cuerpo calloso pero sin lesiones cutáneas. La madre, de 43 años, tiene diagnóstico de SCBCN y no presenta CBCs. Para completar el estudio se realizó secuenciación bidireccional y Multiplex Ligation dependent Probe Amplification (MLPA) en sangre periférica para buscar mutaciones en PTCH1, principal gen responsable del síndrome. Se encontró una mutación germinal novel en el paciente y la madre: una duplicación de 25 pb en el exón 10 (c.1375dupl25bp). El análisis bioinformático predijo un corrimiento del marco de lectura y un codón stop prematuro, que produciría una proteína trunca más corta que lo normal. Nuestros resultados sugieren que el estudio clínico y genealógico completo con análisis genético es fundamental para la detección temprana de casos como el presente.

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) or Gorlin-Goltz syndrome is a rare autosomal dominant disorder, mainly due to PTCH1 gene mutations, that comprises a broad spectrum of clinical manifestations. The presence of multiple basal cell carcinomas (BCCs) is a cardinal sign in NBCCS, therefore cases in which BCCs are absent entails a delay in the diagnosis.We present a 14 years old boy with a clinical diagnosis of NBCCS by the presence of odontogenic cysts, hypertelorism, macrocephaly, and corpus callosum agenesia, but with absence of skin lesions. His 43 years old mother has NBCCS diagnosis and no history of BCCs. For a deeper study, PTCH1 mutation screening from peripheral blood samples were performed by both bidirectional sequencing and multiplex ligation dependent probe amplification (MLPA) techniques. The proband and his mother carry 25 pb duplication in exon 10 (c.1375dupl25bp) that causes a reading frameshift with a premature stop codon. Bioinformatics analysis predicted that this mutation results in a truncated protein shorter than normal. Our results suggest that complete clinical and genealogical studies accompanied by genetic analysis are essential in the early detection of the NBCCS cases such the one presented here.