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Detailed molecular-cytogenetic studies combined with thorough clinical characterization are needed to establish genotype-phenotype correlations for specific chromosome deletion syndromes. Although many patients with subtelomeric deletions have been reported, the phenotype maps for many of the corresponding syndromes, including the terminal deletion 14q syndrome, are only slowly emerging. Here, we report on five patients with terminal partial monosomy of 14q32.3 and characteristic features of terminal deletion 14q syndrome. Four of the patients carry de novo terminal deletions of 14q, three of which have not yet been reported. One patient carries an unbalanced translocation der(14)t(9;14)(q34.3;q32.3). Minimum deletion sizes as determined by molecular karyotyping and FISH are 5.82, 5.56, 4.17, 3.54, and 3.29 Mb, respectively. Based on our findings and a comprehensive review of the literature, we refine the phenotype map for typical clinical findings of the terminal deletion 14q syndrome (i.e., intellectual disability/developmental delay, muscular hypotonia, postnatal growth retardation, microcephaly, congenital heart defects, genitourinary malformations, ocular coloboma, and several dysmorphic signs). Combining this phenotype map with benign copy-number variation data available from the Database of Genomic Variants, we propose a small region critical for certain features of the terminal deletion 14q syndrome which contains only seven RefSeq genes., (Copyright © 2012 Wiley Periodicals, Inc.)

Purpose: Clinical and molecular characterization of patients with horizontal gaze palsy with progressive scoliosis (HGPPS) to extend existing knowledge of the phenotype caused by mutations in the Roundabout homolog of Drosophila 3 (ROBO3) gene., Methods: Four patients (aged 6 months to 13 years), two of them siblings, with features of horizontal gaze palsy and their parents were examined clinically and by molecular testing of the ROBO3 gene. The three families were unrelated, but parents in each family were consanguineous., Results: We identified three novel homozygous ROBO3 mutations in four patients with typical ophthalmologic signs of HGPPS. We found an exonic insertion/deletion mutation (c.913delAinsTGC; p.Ile305CysfsX13), a 31 bp deletion including the donor splice site of exon 17 and adjacent exonic and intronic sequences (c.2769_2779del11, 2779+1_+20del20), and a missense mutation located next to a splice donor site (c.3319A>C) resulting in skipping of exon 22, as shown by cDNA analysis., Conclusions: We describe three novel mutations in the ROBO3 gene and the detailed clinical phenotype of HGPPS. One patient displayed marked convergence upon attempting smooth pursuits to both sides. In one patient, the typical ophthalmologic phenotype, the neuroradiologic findings, and molecular testing led to the diagnosis even before scoliosis developed. In addition to the typical magnetic resonance imaging brain signs of HGPPS, this patient had marked hypoplasia of the frontal lobes and corpus callosum. In summary, diagnosis of HGPPS may be established by ophthalmologic and molecular investigation early in life, allowing ongoing orthopedic surveillance from an early stage.

We extend the spectrum of phenotypes caused by mutations in the Wnt/Norrin coreceptor low-density lipoprotein receptor-related protein 5 (LRP5) by identifying two novel types of mutation in related individuals whose presenting features were profound muscle hypotonia, mild mental retardation, blindness, and growth retardation. One mutation removes 6 out of 9 consecutive leucine residues in the LRP5 signal peptide (c.43_60del or p.Leu15_Leu20del), which impairs polypeptide entry into the endoplasmic reticulum (ER), trafficking to the cell membrane, and signal transduction. The second mutation resulted from nonhomologous recombination between Alu repeat sequences, which deleted exons 14-16 and would produce a nonfunctional, truncated, and frameshifted polypeptide, if expressed [chr11:g.(13871447_1387511)_(13879636_13879700)del (NW_925106.1) or p.Pro1010GlnfsX38]. We confirmed that the length of the LRP5 signal peptide poly-leucine repeat is polymorphic in the general population, and, importantly, we were able to demonstrate in independent in vitro assays that different allele sizes affect receptor processing and signal transduction. Consequently, this polymorphism may have physiologic effects in vivo. This latter finding is relevant since through a genomewide search we identified nearly 400 human proteins that contain poly-leucine repeats within their signal peptide. We chose 18 of these proteins and genotyped the underlying trinucleotide repeat in healthy Caucasian individuals. More than one length allele was observed in one-half of the proteins. We therefore propose that natural variation in poly-leucine-stretches within signal peptides constitutes a currently unrecognized source of variability in protein translation and expression., ((c) 2009 Wiley-Liss, Inc.)

Meckel-Gruber syndrome (MKS) is an autosomal recessive, usually lethal multisystemic disorder characterized by early developmental anomalies of the central nervous system, cystic kidney dysplasia, hepatobiliary ductal plate malformation, and postaxial polydactyly. Three MKS loci have been mapped and recently, two genes were identified: MKS1 on 17q22 in Caucasian kindreds and MKS3 on 8q22 in Omani and Pakistani families, putting MKS on the growing list of ciliary disorders ("ciliopathies"). We performed linkage analysis for MKS1-3 in 14 consanguineous and/or multiplex families of different ethnic origins with histologic diagnosis and at least three classic MKS manifestations in each kindred. Unexpectedly, only five families were linked to any of the known MKS loci, clearly indicating further locus heterogeneity. All five families showed homozygosity for MKS1 and, intriguingly, were of non-Caucasian origin. MKS1 sequencing revealed no mutation in two of these pedigrees, whereas different, novel splicing defects were identified in the three other families and an additional sporadic German patient. Given that all of our mutations and two of the in total four known MKS1 changes cause aberrant splicing (while the other two known mutations were frameshift mutations), we hypothesize that splicing defects are a crucial mutational mechanism in MKS1 which apparently is one of the main loci and key players in MKS. Our results indicate that MKS1 mutations are not restricted to the Caucasian gene pool and suggest further genetic heterogeneity for MKS. Overall, our data have immediate implications for genetic counselling and testing approaches in MKS., ((c) 2007 Wiley-Liss, Inc.)