Fabiana Poerner

Auriculo-condylar syndrome: mapping of a first locus and evidence for genetic heterogeneity

Auriculo-condylar syndrome (ACS), an autosomal dominant disorder of first and second pharyngeal arches, is characterized by malformed ears (‘question mark ears’), prominent cheeks, microstomia, abnormal temporomandibular joint, and mandibular condyle hypoplasia. Penetrance seems to be complete, but there is high inter- and intra-familial phenotypic variation, with no evidence of genetic heterogeneity. We herein describe a new multigeneration family with 11 affected individuals (F1), in whom we confirm intra-familial clinical variability. Facial asymmetry, a clinical feature not highlighted in other ACS reports, was highly prevalent among the patients reported here. The gene responsible for ACS is still unknown and its identification will certainly contribute to the understanding of human craniofacial development. No chromosomal rearrangements have been associated with ACS, thus mapping and positional cloning is the best approach to identify this disease gene. To map the ACS gene, we conducted linkage analysis in two large ACS families, F1 and F2 (F2; reported elsewhere). Through segregation analysis, we first excluded three known loci associated with disorders of first and second pharyngeal arches (Treacher Collins syndrome, oculo-auriculo-vertebral spectrum, and Townes–Brocks syndrome). Next, we performed a wide genome search and we observed evidence of linkage to 1p21.1–q23.3 in F2 (LOD max 3.01 at θ=0). Interestingly, this locus was not linked to the phenotype segregating in F1. Therefore, our results led to the mapping of a first locus of ACS (ACS1) and also showed evidence for genetic heterogeneity, suggesting that there are at least two loci responsible for this phenotype.

Two novel alleles, HLA-B*40:125 and B*40:129, in the Brazilian population

The new alleles, HLA-B*40:125 and HLA-B*40:129, present a mismatch at codon 103.1 (G → C) and three mismatches at codons 9.1 (C → T), 11.1 (T → G) and 12.1 (G → A).

A new allele, HLA-B*4212, identified in a Brazilian volunteer bone marrow donors by sequence-based typing.

Here we report the discovery of a novel HLA‐B allele, named B*4212 in a Brazilian volunteer bone marrow donor. The new sequence has nucleotide variation at position 496 (T→G) as compared with B*4201. This variation results in a conservative amino acid substitution from valine to glycine at codon 165 of exon 3.

Say syndrome : Report of a familial case

We describe a new case of Say syndrome. This syndrome is an autosomal dominant condition characterized by cleft palate, short stature of prenatal onset, large protruding ears and microcephaly, delayed bone age, and renal anomalies. The first report was in 1975 by Say et al. in three generations of a family. Three additional reports of isolated cases were published. Our propositus is a 12-month-old boy with the cardinal signs of the syndrome whose mother has only microcephaly. To our knowledge this is the second familial report with evidence of highly variable expressivity. The occurrence of renal anomalies in a son of a normal sister of his mother suggests incomplete penetrance.

Absence of strong linkage disequilibrium between odorant receptor alleles and the major histocompatibility complex.

The odorant receptor (OR) genes constitute the largest gene family among vertebrates. While over 800 loci are present in the human genome, their allele diversity is still poorly characterized. It has been hypothesized that the products of OR genes can be relevant in the reproductive context, thereby interacting with products of genes of the major histocompatibility complex (MHC). Here we investigated the genetic diversity of the OR2W6P, OR2B8P, OR1F12 and OR12D2 genes, in order to define haplotypes and haplotype frequencies. We measured levels of linkage disequilibrium (LD) between these OR genes and the MHC genes HLA-A, HLA-B and HLA-DRB1. This was accomplished through the assessment of 30 single nucleotide polymorphisms (SNPs) in samples from 61 family trios. We characterized 26 alleles among the four OR genes and identified three SNPs that had not yet been reported. Based on our haplotype analysis, LD spanning the OR-HLA region is not very strong, and therefore not enough to enable selection regarding specific HLA-OR haplotypes.

Identification of a novel HLA-A allele, HLA-A*0355, in a Brazilian family of eastern European descendents

The new human leukocyte antigen (HLA) class I allele, HLA-A*0355 was identified in a Brazilian family. Our sequence analysis detected a mismatch located in exon 2, codon 86, at position 258 (C-->A) that results in a nonsilent and nonconservative substitution with the replacement of asparagine by lysine. Substitutions located at this oligosaccharide attachment site of the protein were observed in only other four classic HLA class I sequences, indicating a highly conserved peptide site however its function remains unknown.