Ferda E. Percin

LRP4 Mutations Alter Wnt/β-Catenin Signaling and Cause Limb and Kidney Malformations in Cenani-Lenz Syndrome

Cenani-Lenz syndrome (CLS) is an autosomal-recessive congenital disorder affecting distal limb development. It is characterized mainly by syndactyly and/or oligodactyly and is now shown to be commonly associated with kidney anomalies. We used a homozygosity-mapping approach to map the CLS1 locus to chromosome 11p11.2-q13.1. By sequencing candidate genes, we identified recessive LRP4 mutations in 12 families with CLS. LRP4 belongs to the low-density lipoprotein (LDL) receptor-related proteins (LRPs), which are essential for various developmental processes. LRP4 is known to antagonize LRP6-mediated activation of canonical Wnt signaling, a function that is lost by the identified mutations. Our findings increase the spectrum of congenital anomalies associated with abnormal lipoprotein receptor-dependent signaling.

Lrp4 Regulates Initiation of Ureteric Budding and Is Crucial for Kidney Formation - A Mouse Model for Cenani-Lenz Syndrome

BACKGROUND Development of the kidney is initiated when the ureteric bud (UB) branches from the Wolffian duct and invades the overlying metanephric mesenchyme (MM) triggering the mesenchymal/epithelial interactions that are the basis of organ formation. Multiple signaling pathways must be integrated to ensure proper timing and location of the ureteric bud formation. METHODS AND PRINCIPAL FINDINGS We have used gene targeting to create an Lrp4 null mouse line. The mutation results in early embryonic lethality with a subpenetrant phenotype of kidney agenesis. Ureteric budding is delayed with a failure to stimulate the metanephric mesenchyme in a timely manner, resulting in failure of cellular differentiation and resulting absence of kidney formation in the mouse as well as comparable malformations in humans with Cenani-Lenz syndrome. CONCLUSION Lrp4 is a multi-functional receptor implicated in the regulation of several molecular pathways, including Wnt and Bmp signaling. Lrp4(-/-) mice show a delay in ureteric bud formation that results in unilateral or bilateral kidney agenesis. These data indicate that Lrp4 is a critical regulator of UB branching and lack of Lrp4 results in congenital kidney malformations in humans and mice.

Association of microsomal epoxide hydrolase gene polymorphism and pre‐eclampsia in Turkish women

Aim:  To assess the association between human epoxide hydrolase exon 3 and 4 polymorphisms and pre‐eclampsia by carrying out a case‐control study in Turkish women.

Autosomal recessive mesoaxial synostotic syndactyly with phalangeal reduction maps to chromosome 17p13.3

Previously we have described a novel and distinct form of non‐syndromic osseous syndactyly segregating in an autosomal recessive pattern in a consanguineous Pakistani family. The limb findings include mesoaxial reduction of the fingers, synostoses of the third and fourth metacarpals with associated single phalanges, fifth finger clinodactyly, and preaxial webbing of toes. We identified another published report of this phenotype in a large, inbred Turkish family. In the present study we mapped the phenotype in the Pakistani and Turkish families to chromosome 17p13.3 (multipoint LOD score 5.1). The identification of a single locus for this complex limb malformation in two families with distinct ethnic backgrounds supports the hypothesis that this is a distinct form of syndactyly. Since this form of syndactyly is phenotypically distinct from the previously described eight types, we propose to name this phenotype mesoaxial synostotic syndactyly with phalangeal reduction (MSSD, type IX syndactyly, Malik–Percin type).

TMCO1 deficiency causes autosomal recessive cerebrofaciothoracic dysplasia.

Cerebrofaciothoracic dysplasia (CFT) (OMIM #213980) is a multiple congenital anomaly and intellectual disability syndrome involving the cranium, face, and thorax. The characteristic features are cranial involvement with macrocrania at birth, brachycephaly, various CT/MRI findings including hypoplasia of corpus callosum, enlargement of septum pellicidum, and diffuse hypodensity of the grey matter, flat face, hypertelorism, cleft lip and cleft palate, low‐set, posteriorly rotated ears, short neck, and multiple costal and vertebral anomalies. The underlying genetic defect remains unknown. Using combination of homozygosity mapping and whole‐exome sequencing, we identified a homozygous nonsense founder mutation, p.Arg87Ter (c.259 C>T), in the human transmembrane and coiled‐coil domains protein 1 (TMCO1) in four out of five families of Turkish origin. The entire critical region on chromosome 1q24 containing TMCO1 was excluded in the fifth family with characteristic findings of CFT providing evidence for genetic heterogeneity of CFT spectrum. Another founder TMCO1 mutation has recently been reported to cause a unique genetic condition, TMCO1‐defect syndrome (OMIM #614132). TMCO1‐defect syndrome shares many features with CFT. This study supports the fact that “TMCO1‐defect syndrome,” initially thought to represent a distinct disorder, indeed belongs to the genetically heterogeneous CFT dysplasia spectrum.

A Turkish family with Nance-Horan syndrome due to a novel mutation

Nance-Horan Syndrome (NHS) is a rare X-linked syndrome characterized by congenital cataract which leads to profound vision loss, characteristic dysmorphic features and specific dental anomalies. Microcornea, microphthalmia and mild or moderate mental retardation may accompany these features. Heterozygous females often manifest similarly but with less severe features than affected males. We describe two brothers who have the NHS phenotype and their carrier mother who had microcornea but not cataract. We identified a previously unreported frameshift mutation (c.558insA) in exon 1 of the NHS gene in these patients and their mother which is predicted to result in the incorporation of 11 aberrant amino acids prior to a stop codon (p.E186Efs11X). We also discussed genotype-phenotype correlation according to relevant literature.

No association of polymorphisms in the glutathione S-transferase genes with pre-eclampsia, eclampsia and HELLP syndrome in a Turkish population

Aim: There is substantial evidence that genetic factors play a role in pre‐eclampsia. The aim of this study was to determine whether genetic variability in the encoding of genes for glutathione S‐transferase M1 (GSTM1) and glutathione S‐transferase T1 (GSTT1) contributes to individual differences in susceptibility to pre‐eclampsia, eclampsia, or hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome).

Fibrillin-1 gene intron 56 polymorphism in Turkish children with mitral valve prolapse.

OBJECTIVE Mitral valvar prolapse is the most common anomaly of the mitral valve apparatus throughout childhood. Fibrillin is one of the structural components of the elastin-associated microfibrils found in the mitral valve. A case-controlled study has performed to investigate the relationship between fibrillin 1 gene intron 56 polymorphism and risk of mitral valvar prolapse in Turkish children. PATIENTS AND METHODS A total of 77 patients with mitral valvar prolapse diagnosed by clinical evaluation and echocardiography and 89 normal children of same age and sex were studied. The fibrillin-1 gene intron 56 polymorphism was identified by the polymerase chain reaction-based restriction analysis. RESULTS There was a significant difference in the distribution of fibrillin-1 gene intron 56 genotypes (p = 0.0001) and allelic frequency (p = 0.0001) between the cases and the controls. CONCLUSIONS Patients with mitral valvar prolapse have higher frequencies of fibrillin-1 gene intron 56 GC genotypes. Healthy children have higher frequencies of fibrillin-1 gene intron 56 CC genotypes. We speculate that the higher frequency of fibrillin-1 gene intron 56 G-allele increases the risk of mitral valvar prolapse.

Duplication 4q associated with chronic cholestatic changes in liver biopsy.

We report a 15-day-old girl with partial trisomy 4q syndrome who presented with neonatal cholestasis. She had dysmorphic facial features and preaxial polysyndactyly of the right hand. The other findings were generalized hypertrichosis, pes equinovarus, oedema on feet and mild hepatomegaly. No specific reason for the cholestasis with elevated liver enzymes and direct bilirubinemia were characterized. Cytogenetic analyses revealed a karyotype 46,XX,der(13)t(4;13)(q25;p13). This is the first patient with partial trisomy 4q syndrome presented with neonatal cholestasis.

Rectal duplications accompanying rectovestibular fistula: Report of two cases

Rectal duplication (RD) cysts are rare congenital anomalies that can be diagnosed with the presence of another opening in the perineum. They seldom accompany anorectal malformations (ARM). Two cases of RD accompanying ARM at opposite ends of the phenotypic spectrum, are described. A 3‐month‐old baby and a 2‐year‐old girl with ARM were scheduled for posterior sagittal anorectoplasty. The infant had an orifice at the anal dimple and the other had an orifice at the vestibulum posterior to the rectovestibular fistula. The infant presented with no other anomalies whereas the older one presented with an unusual coexistence of caudal duplication and caudal regression syndromes. Perioperatively both orifices were found to be related to retrorectal cysts, and were excised. Clinicians should always be alert when dealing with complex malformations. Because these malformations have variable anatomical and clinical presentations, they can represent a diagnostic and therapeutic challenge.