Brazilian Pedigree Research Articles

Frequency and origin of the c.2090T>G p.(Leu697Trp) MYO3A variant associated with autosomal dominant hearing loss.

We recently described a novel missense variant [c.2090T>G:p.(Leu697Trp)] in the MYO3A gene, found in two Brazilian families with late-onset autosomal dominant nonsyndromic hearing loss (ADNSHL). Since then, with the objective of evaluating its contribution to ADNSHL in Brazil, the variant was screened in additional 101 pedigrees with probable ADNSHL without conclusive molecular diagnosis. The variant was found in three additional families, explaining 3/101 (~3%) of cases with ADNSHL in our Brazilian pedigree collection. In order to identify the origin of the variant, 21 individuals from the five families were genotyped with a high-density SNP array (~600 K SNPs- Axiom Human Origins; ThermoFisher). The identity by descent (IBD) approach revealed that many pairs of individuals from the different families have a kinship coefficient equivalent to that of second cousins, and all share a minimum haplotype of ~607 kb which includes the c.2090T>G variant suggesting it probably arose in a common ancestor. We inferred that the mutation occurred in a chromosomal segment of European ancestry and the time since the most common ancestor was estimated in 1100 years (CI = 775-1425). This variant was also reported in a Dutch family, which shares a 87,121 bp haplotype with theBrazilian samples, suggesting that Dutch colonists may have brought it to Northeastern Brazil in the 17th century. Therefore, the present study opens new avenues to investigate this variant not only in Brazilians but also in European families with ADNSHL.

Novel partial duplication of EYA1 causes branchiootic syndrome in a large Brazilian family

Objective: To identify novel genetic causes of syndromic hearing loss in Brazil. Design: To map a candidate chromosomal region through linkage studies in an extensive Brazilian family and identify novel pathogenic variants using sequencing and array-CGH. Study sample: Brazilian pedigree with individuals affected by BO syndrome characterized by deafness and malformations of outer, middle and inner ear, auricular and cervical fistulae, but no renal abnormalities. Results: Whole genome microarray-SNP scanning on samples of 11 affected individuals detected a multipoint Lod score of 2.6 in the EYA1 gene region (chromosome 8). Sequencing of EYA1 in affected patients did not reveal pathogenic mutations. However, oligonucleotide-array-CGH detected a duplication of 71.8Kb involving exons 4 to 10 of EYA1 (heterozygous state). Real-time-PCR confirmed the duplication in fourteen of fifteen affected individuals and absence in 13 unaffected individuals. The exception involved a consanguineous parentage and was assumed to involve a different genetic mechanism. Conclusions: Our findings implicate this EYA1 partial duplication segregating with BO phenotype in a Brazilian pedigree and is the first description of a large duplication leading to the BOR/BO syndrome.

Neuron-Specific Enolase Is Elevated in Asymptomatic Carriers of Leber's Hereditary Optic Neuropathy

Neuron-specific enolase (NSE) is a biomarker for neuronal stress. Leber's hereditary optic neuropathy (LHON) is a mitochondrial disease affecting retinal ganglion cells (RGC). These RGCs and their axons in the retinal nerve fiber layer (RNFL) and optic nerve head may show subclinical pathology in unaffected mutation carriers, or undergo cell death in affected patients. We hypothesize that increased levels of blood NSE may characterize LHON carriers as a biomarker of ongoing RGC stress. Serum was obtained from 74 members of a Brazilian pedigree with LHON carrying the homoplasmic 11778/ND4 mitochondrial DNA mutation. Classified by symptoms and psychophysical metrics, 46/74 patients were unaffected mutation "carriers," 14/74 were "affected," and 14/74 were "off-pedigree" controls. Serum NSE levels were determined by ELISA specific for the γ subunit of NSE. Serum NSE concentrations in carriers (27.17 ± 39.82 μg/L) were significantly higher than affected (5.66 ± 4.19 μg/L; P = 0.050) and off-pedigree controls (6.20 ± 2.35 μg/L; P = 0.047). Of the 14/46 (30.4 %) carriers with significantly elevated NSE levels (mean = 75.8 ± 42.3 μg/L), 9/14 (64.3%) were male. Furthermore, NSE levels were nearly three times greater in asymptomatic male carriers (40.65 ± 51.21 μg/L) than in asymptomatic female carriers (15.85 ± 22.27 μg/L; P = 0.034). Serum NSE levels are higher in LHON carriers compared with affected and off-pedigree individuals. A subgroup of mostly male carriers had significantly elevated serum NSE levels. Thus, male carriers are at higher risk for LHON-related neuronal stress.

Visual evoked potentials findings in non-affected subjects from a large Brazilian pedigree of 11778 Leber’s hereditary optic neuropathy

To investigate pattern-reversal visual evoked potentials (PRVEP) in asymptomatic maternally and non-maternally related members from a large Brazilian 11778/ND4 LHON pedigree. Transient PRVEP for check sizes 15' and 60' were recorded from asymptomatic mutation carriers and non-mutant descendants of affected/non-affected males, all with best-corrected visual acuity of 20/20. A control group of spouses (off-pedigree) was also included. Parameters of N75, P100 and N135 latencies (ms) and N75-P100 peak-to-peak amplitude (μV) as well as temporal dispersion (latency of N135-latency of N75) were determined. Longitudinal testing was obtained in a subseries of carriers in three annual consecutive visits. We tested 48 asymptomatic mutation carriers, 19 descendants of affected males, 9 descendants of non-affected males and 27 off-pedigrees, all of the latter being non-mutant. All non-mutant male descendants did not differ from off-pedigree controls. Statistically prolonged P100 latencies were found in mutation carriers (P=0.0143) when compared with off-pedigrees for check sizes 15', as well as significantly larger temporal dispersions for both check size 15' (P=0.0012) and check size 60' (P=0.0271). Serial testing in 15 mutation carriers disclosed prolonged P100 latencies and larger temporal dispersion that did not change over time. Subclinical PRVEP abnormalities were detected in this large group of asymptomatic carriers of the 11778/ND4 LHON mutation from the same family, confirming and extending previous psychophysical and structural findings of a selective involvement of the parvocellular pathway. PRVEP is a useful test to characterize and monitor visual dysfunction in this devastating disease.

Multiple endocrine neoplasia type 1 in Brazil: MEN1 founding mutation, clinical features, and bone mineral density profile

Only few large families with multiple endocrine neoplasia type 1 (MEN1) have been documented. Here, we aimed to investigate the clinical features of a seven-generation Brazilian pedigree, which included 715 at-risk family members. Genealogical and geographic analysis was used to identify the MEN1 pedigree. Clinical and genetic approach was applied to characterize the phenotypic and genotypic features of the family members. Our genetic data indicated that a founding mutation in the MEN1 gene has occurred in this extended Brazilian family. Fifty family members were diagnosed with MEN1. Very high frequencies of functioning and non-functioning MEN1-related tumors were documented and the prevalence of prolactinoma (29.6%) was similar to that previously described in prolactinoma-variant Burin (32%). In addition, bone mineral density analysis revealed severe osteoporosis (T, -2.87+/-0.32) of compact bone (distal radius) in hyperparathyroidism (HPT)/MEN1 patients, while marked bone mineral loss in the lumbar spine (T, -1.95+/-0.39), with most cancellous bone, and femoral neck (mixed composition; T, -1.48+/-0.27) were also present. In this study, we described clinically and genetically the fifth largest MEN1 family in the literature. Our data confirm previous findings suggesting that prevalence of MEN1-related tumors in large families may differ from reports combining cumulative data of small families. Furthermore, we were able to evaluate the bone status in HPT/MEN1 cases, a subject that has been incompletely approached in the literature. We discussed the bone loss pattern found in our MEN1 patients comparing with that of patients with sporadic primary HPT.

Erratum: Unexpected genetic heterogeneity in a large consanguineous Brazilian pedigree presenting deafness

Correction to: European Journal of Human Genetics (2008) 16, 89–96; doi:10.1038/sj.ejhg.5201917; published online 12 September 2007 Since the publication of the above paper, the authors have identified three typographical errors regarding Table 1. The amended table is shown below.

Linkage to chromosome 2q36.1 in autosomal dominant Dandy-Walker malformation with occipital cephalocele and evidence for genetic heterogeneity

We previously reported a Vietnamese-American family with isolated autosomal dominant occipital cephalocele. Upon further neuroimaging studies, we have recharacterized this condition as autosomal dominant Dandy-Walker with occipital cephalocele (ADDWOC). A similar ADDWOC family from Brazil was also recently described. To determine the genetic etiology of ADDWOC, we performed genome-wide linkage analysis on members of the Vietnamese-American and Brazilian pedigrees. Linkage analysis of the Vietnamese-American family identified the ADDWOC causative locus on chromosome 2q36.1 with a multipoint parametric LOD score of 3.3, while haplotype analysis refined the locus to 1.1 Mb. Sequencing of the five known genes in this locus did not identify any protein-altering mutations. However, a terminal deletion of chromosome 2 in a patient with an isolated case of Dandy-Walker malformation also encompassed the 2q36.1 chromosomal region. The Brazilian pedigree did not show linkage to this 2q36.1 region. Taken together, these results demonstrate a locus for ADDWOC on 2q36.1 and also suggest locus heterogeneity for ADDWOC.

Recurrent KIND1 (C20orf42) gene mutation, c.676insC, in a Brazilian pedigree with Kindler syndrome

Recurrent KIND1 (C20orf42) gene mutation, c.676insC, in a Brazilian pedigree with Kindler syndrome

A multi-exonic SPG4 duplication underlies sex-dependent penetrance of hereditary spastic paraplegia in a large Brazilian pedigree

SPG4 mutations are the most frequent cause of autosomal-dominant hereditary spastic paraplegia (HSP). SPG4 HSP is characterized by large inter- and intrafamilial variability in age at onset (AAO) and disease severity. The broad spectrum of SPG4 mutations has recently been further extended by the finding of large genomic deletions in SPG4-linked pedigrees negative for 'small' mutations. We had previously reported a very large pedigree, linked to the SPG4 locus with many affected members, which showed gender difference in clinical manifestation. Screening for copy number aberrations revealed the first case of a multi-exonic duplication (exon10_12dup) in the SPG4 gene. The mutation leads to a premature stop codon, suggesting that the protein product is not functional. The analysis of 30 individuals who carry the mutation showed that males have on average an earlier AAO and are more severely affected. The present family suggests that this HSP pathogenesis may be modulated by factors related to individual background and gender as observed for other autosomal dominant conditions, such as facio-scapulohumeral muscular dystrophy or amyloidosis. Understanding why some individuals, particularly women, are 'partially protected' from the effects of this and other pathogenic mutations is of utmost importance.

Unexpected genetic heterogeneity in a large consanguineous Brazilian pedigree presenting deafness

Nonsyndromic autosomal recessive deafness accounts for 80% of hereditary deafness. To date, 52 loci responsible for autosomal recessive deafness have been mapped and 24 genes identified. Here, we report a large inbred Brazilian pedigree with 26 subjects affected by prelingual deafness. Given the extensive consanguinity found in this pedigree, the most probable pattern of inheritance is autosomal recessive. However, our linkage and mutational analysis revealed, instead of an expected homozygous mutation in a single gene, two different mutant alleles and a possible third undetected mutant allele in the MYO15A gene (DFNB3 locus), as well as evidence for other causes for deafness in the same pedigree. Among the 26 affected subjects, 15 were homozygous for the novel c.10573delA mutation in the MYO15A gene, 5 were compound heterozygous for the mutation c.10573delA and the novel deletion c.9957_9960delTGAC and one inherited only a single c.10573delA mutant allele, while the other one could not be identified. Given the extensive consanguinity of the pedigree, there might be at least one more deafness locus segregating to explain the condition in some of the subjects whose deafness is not clearly associated with MYO15A mutations, although overlooked environmental causes could not be ruled out. Our findings illustrate a high level of etiological heterogeneity for deafness in the family and highlight some of the pitfalls of genetic analysis of large genes in extended pedigrees, when homozygosity for a single mutant allele is expected.

Chromatic and Luminance Contrast Sensitivities in Asymptomatic Carriers from a Large Brazilian Pedigree of 11778 Leber Hereditary Optic Neuropathy

To determine whether asymptomatic 11778 LHON carriers demonstrated impairments in (1) chromatic red/green (R/G) and blue/yellow (B/Y) contrast sensitivity functions (CSF) and in (2) luminance contrast sensitivity functions in the spatial CSF (SCSF) and temporal CSF (TCSF) domains. Twenty-five carriers (8 male, 17 female; 34.1 +/- 15.1 years of age) of homoplasmic 11778 LHON from the same well-described family and 30 age-matched controls (17 male, 13 female; 29.2 +/- 7.1 years of age) were tested in one eye, randomly selected. Of the 25 eyes tested, 18 had normal fundus, 5 had swelling and microangiopathy, and 2 had temporal pallor. The R/G and B/Y CSFs were obtained after equiluminance correction with bichromatic horizontal sinusoidal gratings at 0.3, 0.7, and 2 cycles per degree (cpd); the SCSFs were obtained with achromatic gratings at 0.3, 2, 6, and 12 cpd; and the TCSFs were obtained at 2, 10, 20, and 33 Hz with sinusoidal modulation of a 2.7 degrees field with a superimposed spatial Gabor function. Differences between carriers and controls were statistically significant for all spatial frequencies of chromatic and luminance SCSFs, but not for the TCSFs. R/G equiluminance settings of carriers differed from those of controls (P < 0.001), requiring higher luminance in the green; B/Y equiluminance settings were not statistically different in carriers and controls. Fundus findings did not correlate with CS results. Luminance and chromatic spatial CS losses that affected all tested spatial frequencies, are reported in LHON asymptomatic carriers with the mtDNA 11778 mutation. No losses were found in the temporal CSF. An intriguing finding is that the blue system is substantially spared in this LHON family. These represent subclinical visual impairments in otherwise asymptomatic LHON carriers.

A very large Brazilian pedigree with 11778 Leber’s hereditary optic neuropathy. Sadun AA, Carelli V, Saomao SR, Berezovsky A, Quiros P, Sadun F, DeNegri AM, Andrade R, Schein S, Belfort R. Trans Am Ophthalmol Soc 2003;100:169–180

The authors conducted an extensive epidemiological, neuro-ophthlamological, psychophysical, and blood examination on a newly discovered, very large pedigree with molecular analysis showing mtDNA mutation for Leber hereditary optic neuropathy (LHON). Four index cases from a remote area of Brazil were sent to Sao Paulo, where complete ophthalmological examination strongly suggested LHON. Molecular analysis of their blood demonstrated that they were LHON, homoplasmic 11778, J-haplogroup. They had an extensive family that all lived in one rural area in Brazil. To investigate this family, we drew on a number of international experts to form a team that traveled to Brazil. This field team also included several members of the Federal University of Sao Paulo, and together the authors investigated 273 of the 295 family members that were still alive. Epidemiological interviews, comprehensive neuro-ophthalmological examinations, psychophysical tests, Humphrey visual fields, fundus photographs, and blood testing for mitochondrial mutations and nuclear gene linkage were performed. Nearly 95% of the pedigree with LHON 11778 were comprehensively studied. The person representing the first-generation case migrated from Verona, Italy, to Colatina, Brazil. Subsequent generations demonstrated penetrance rates of 71%, 60%, 34%, 15%, and 9%. The percentages of males were 60%, 50%, 64%, 100%, and 100%. Age at onset varied from 10 to 64 years, and current visual acuities varied from light perception to 20/400. Analysis of environmental risk factors and a nuclear modifying factor from this group may help address the clinical observation that only some of genetically affected individuals manifest the disease.—Hans E. Grossniklaus

Extensive investigation of a large Brazilian pedigree of 11778/haplogroup J Leber hereditary optic neuropathy

Purpose To conduct systematic epidemiologic, neuro-ophthalmologic, psychophysical, and mitochondrial DNA (mtDNA) genetic examinations on a newly identified pedigree with Leber hereditary optic neuropathy (LHON). Design Observational population cohort study. Methods A prospective investigation of an entire Brazilian LHON family. Setting A field investigation by an international team conducted in a remote part of Brazil. Study population We evaluated 265 (both eyes) of the 328 living family members of this LHON pedigree. Only members of this pedigree were studied. Those entering the pedigree as spouses were used as controls. Observation procedures We conducted epidemiologic interviews emphasizing possible environmental risk factors, comprehensive neuro-ophthalmologic examinations, psychophysical tests, Humphrey visual field studies, fundus photography, and blood testing for mitochondrial genetic analysis. Results We reconstructed a seven-generation maternal lineage descended from a common ancestor dating to the 1870s. All maternally related family members were invariably homoplasmic 11778 with a haplogroup J mtDNA, 33 being affected, of which 22 are still living. With each subsequent generation, there was a progressive decrease of penetrance, and only males were affected in the last two generations. A significant exposure (greater than 95% confidence intervals) to a variety of environmental risk factors characterized the affected individuals, with smoking as the most common ( P < .01). Both affected and carriers (95% confidence intervals) presented with a significantly lower incidence of hypertension and high cholesterol compared with the control group ( P < .05). Conclusions Almost 95% of a 328-living-member pedigree with LHON 11778/J haplogroup was comprehensively studied. Our initial results indicate the strong influence of environmental risk factors. The remarkably reduced incidence of cardiovascular risk in the maternal lineage is discussed. Further genetic analysis may reveal a role for the nuclear genome.