Mehmet Alikasifoglu

Mutations in the Gene Encoding the RER Protein FKBP65 Cause Autosomal-Recessive Osteogenesis Imperfecta

Osteogenesis imperfecta is a clinically and genetically heterogeneous brittle bone disorder that results from defects in the synthesis, structure, or posttranslational modification of type I procollagen. Dominant forms of OI result from mutations in COL1A1 or COL1A2, which encode the chains of the type I procollagen heterotrimer. The mildest form of OI typically results from diminished synthesis of structurally normal type I procollagen, whereas moderately severe to lethal forms of OI usually result from structural defects in one of the type I procollagen chains. Recessively inherited OI, usually phenotypically severe, has recently been shown to result from defects in the prolyl-3-hydroxylase complex that lead to the absence of a single 3-hydroxyproline at residue 986 of the alpha1(I) triple helical domain. We studied a cohort of five consanguineous Turkish families, originating from the Black Sea region of Turkey, with moderately severe recessively inherited OI and identified a novel locus for OI on chromosome 17. In these families, and in a Mexican-American family, homozygosity for mutations in FKBP10, which encodes FKBP65, a chaperone that participates in type I procollagen folding, was identified. Further, we determined that FKBP10 mutations affect type I procollagen secretion. These findings identify a previously unrecognized mechanism in the pathogenesis of OI.

Disruption of ALX1 Causes Extreme Microphthalmia and Severe Facial Clefting: Expanding the Spectrum of Autosomal-Recessive ALX-Related Frontonasal Dysplasia

We present an autosomal-recessive frontonasal dysplasia (FND) characterized by bilateral extreme microphthalmia, bilateral oblique facial cleft, complete cleft palate, hypertelorism, wide nasal bridge with hypoplasia of the ala nasi, and low-set, posteriorly rotated ears in two distinct families. Using Affymetrix 250K SNP array genotyping and homozygosity mapping, we mapped this clinical entity to chromosome 12q21. In one of the families, three siblings were affected, and CNV analysis of the critical region showed a homozygous 3.7 Mb deletion containing the ALX1 (CART1) gene, which encodes the aristaless-like homeobox 1 transcription factor. In the second family we identified a homozygous donor-splice-site mutation (c.531+1G > A) in the ALX1 gene, providing evidence that complete loss of function of ALX1 protein causes severe disruption of early craniofacial development. Unlike loss of its murine ortholog, loss of human ALX1 does not result in neural-tube defects; however, it does severely affect the orchestrated fusion between frontonasal, nasomedial, nasolateral, and maxillary processes during early-stage embryogenesis. This study further expands the spectrum of the recently recognized autosomal-recessive ALX-related FND phenotype in humans.

Implications of certain genetic polymorphisms in scarring in vesicoureteric reflux: Importance of ace polymorphism

Polymorphisms of the renin-angiotensin system (RAS) have been shown to affect renal prognosis in a number of diseases. We examined the influence of deletion (D) and insertion (I) polymorphism in the angiotensin I-converting enzyme (ACE) gene and the other polymorphic markers of RAS, and that of plasminogen-activator inhibitor-1 (PAI-1) on renal scarring in reflux nephropathy. Ninety-four children with third- or fourth-degree reflux were the subject of the study. They were stratified into two groups according to the technetium-99m-dimercaptosuccinic acid (DMSA) findings: the first group consisted of 41 patients with no scar formation. In the second group (n = 53), there was significant scar formation in the refluxing units. ACE levels, ACE gene, angiotensin-1 receptor (AT1) A1166C, angiotensinogen (ATG) M235T, and PAI-1 4G/5G polymorphisms were studied. In the second group with scarred kidneys, 18 patients had decreased renal function. The frequency of patients homozygous for the D allele was significantly greater in the second group with scar formation in the refluxing units compared with the first group of patients (P < 0.005). On multivariate analysis, the DD genotype was the only factor that had a significant impact on renal scar formation, introducing a 4.9-fold risk (P < 0.05, 95% confidence interval). We were unable to find any correlation with the presence ofDD genotype and hypertension, decreased renal function, proteinuria, or sex of the patient. DDgenotype correlated with the serum ACE levels (P < 0.005). AT1and ATGpolymorphisms and PAI-1 polymorphism did not correlate with scar formation or any of the parameters. This study provides evidence that the DDgenotype of ACE may be a genetic susceptibility factor contributing to adverse renal prognosis in reflux nephropathy; namely, scar formation. The role of the synergism between the aforementioned genetic polymorphisms can be enlightened with larger patient groups, possibly through multicenter studies.

ALX4 dysfunction disrupts craniofacial and epidermal development

Genetic control of craniofacial morphogenesis requires a complex interaction of numerous genes encoding factors essential for patterning and differentiation. We present two Turkish families with a new autosomal recessive frontofacial dysostosis syndrome characterized by total alopecia, a large skull defect, coronal craniosynostosis, hypertelorism, severely depressed nasal bridge and ridge, bifid nasal tip, hypogonadism, callosal body agenesis and mental retardation. Using homozygosity mapping, we mapped the entity to chromosome 11p11.2-q12.3 and subsequently identified a homozygous c.793C-->T nonsense mutation in the human ortholog of the mouse aristaless-like homeobox 4 (ALX4) gene. This mutation is predicted to result in a premature stop codon (p.R265X) of ALX4 truncating 146 amino acids of the protein including a part of the highly conserved homeodomain and the C-terminal paired tail domain. Although the RNA is stable and not degraded by nonsense-mediated RNA decay, the mutant protein is likely to be non-functional. In a skin biopsy of an affected individual, we observed a hypomorphic interfollicular epidermis with reduced suprabasal layers associated with impaired interfollicular epidermal differentiation. Hair follicle-like structures were present but showed altered differentiation. Our data indicate that ALX4 plays a critical role both in craniofacial development as in skin and hair follicle development in human.

Higher frequency of allele 2 of the interleukin-1 receptor antagonist gene in patients with juvenile idiopathic arthritis.

OBJECTIVE An increased incidence of allele 2 of the interleukin-1 receptor antagonist gene (IL1RN*2) in several inflammatory diseases has recently been reported. The aim of this study was to examine a variable number tandem repeat (VNTR) polymorphism of the IL1RN gene in patients with juvenile idiopathic arthritis (JIA). METHODS Findings in 185 Czech patients with JIA were compared with those in 168 Czech controls, 50 JIA patients and 52 controls of Turkish origin, and 79 controls from central England. VNTR polymorphism analysis of IL1RN was performed by polymerase chain reaction using 2 flanking primers to amplify an 86-bp tandem repeat region in intron 2. RESULTS The frequency and carriage rate of IL1RN*2 were significantly increased in Czech JIA patients compared with the Czech controls (frequency 27.6% versus 15.8%; carriage rate 44.3% versus 26.2%). Increased frequency and carriage rate of IL1RN*2 were found in 23.3% and 40.0% of Turkish JIA patients and in 17.3% and 34.6% of ethnically matched controls. The high representation of IL1RN*2 in 52.3% of the 22 patients with extended oligoarthritis, 31.3% of the 56 patients with enthesitis-related arthritis, and 42.9% of the 14 patients with other arthritis was particularly responsible for the increased frequency of IL1RN*2 in the Czech JIA patients. We found no association of IL1RN*2 with disease activity or severity parameters. CONCLUSION Inheritance of IL1RN*2 may contribute to genetic susceptibility in several forms of autoimmune diseases, including JIA. The IL1RN*2 allele may be useful as a prognostic indicator of the evolution of an extended oligoarticular course of JIA.

Association of the 677C-->T mutation on the methylenetetrahydrofolate reductase gene in Turkish patients with neural tube defects.

We report the analysis of the 677C→T mutation on the 5,10-methylenetetrahydrofolate reductase gene in Turkish controls and cases of neural tube defects. Mutation analysis of 91 patients with neural tube defects, 72 mothers, 63 fathers, and 93 healthy controls has been made by polymerase chain reaction and allele specific restriction digestion with Hinf I. We did not find a significant difference in the 677C→T allele and genotype distribution among the patients with neural tube defects, their parents, and the control group. This result suggests that another mutation in the folate-related enzyme genes could be responsible for neural tube defects in Turkey. None of the mothers of patients with neural tube defects was advised to use folic acid as recommended to prevent neural tube defects. An immediate attempt to establish an education program for healthcare providers and women of childbearing age is crucial in Turkey. Furthermore, fortification of foods with folate would be a better approach. (J Child Neurol 1999;14:159-161).

A Homozygous Deletion in GRID2 Causes a Human Phenotype With Cerebellar Ataxia and Atrophy

GRID2 is a member of the ionotropic glutamate receptor family of excitatory neurotransmitter receptors. GRID2 encodes the glutamate receptor subunit delta-2, selectively expressed in cerebellar Purkinje cells. The phenotype associated with loss of GRID2 function was described only in mice until now, characterized by different degrees of cerebellar ataxia and usually relatively mild abnormalities of the cerebellum. This work describes for the first time the human phenotype associated with homozygous partial deletion of GRID2 in 3 children in one large consanguineous Turkish family. Homozygous deletion of exons 3 and 4 of GRID2 (94 153 589-94 298 037 bp) in the proband and similarly affected cousins, and heterozygous deletions in parental DNA were shown using Affymetrix® 6.0 single-nucleotide polymorphism array, confirmed by real-time polymerase chain reaction. The phenotype includes nystagmus, hypotonia with marked developmental delay in gross motor skills in early infancy followed by a static encephalopathy course with development of cerebellar ataxia, oculomotor apraxia, and pyramidal tract involvement.

Variable pathogenicity of exon 43del (FAA) in four Fanconi anaemia patients within a consanguineous family

Four Fanconi anaemia group A (FAA) patients within two related consanguineous families are presented: the propositus (male, 13 years, transplanted at age 10), and his three cousins (one male, 8 years, and two female newborns). Assignment of the patients to FAA was based on the functional complementation analysis by somatic cell hybridization and confirmed by mutation screening showing a homozygous deletion of exon 43 (4267–4404del) in the FAA gene to be present in all four patients. The newborn patients had been diagnosed prenatally by DNA analysis. In spite of identical molecular pathology and close familial relationship the clinical phenotypes of the four patients were not concordant. Discordant symptoms included birthweight, pigmentation abnormalities, skeletal, renal and genital abnormalities, whereas microcephaly and possibly the haematological course were concordant. Differences in environmental conditions and/or genetic make‐up along with chance effects during development may explain discordant phenotypes despite identical molecular pathology in these patients. However, our results do not rule out the possibility that the exon 43del mutation may have prognostic value for the haematological course of the disease.

A Case Series of Adenosine Deaminase 2-deficient Patients Emphasizing Treatment and Genotype-phenotype Correlations.

To the Editor: Deficiency of adenosine deaminase 2 (DADA2) causes a vasculopathy with autoinflammatory features associated with mutations in CECR1 1. The phenotype of DADA2 varies from only cutaneous lesions to full-blown systemic disease with central nervous system (CNS) involvement and aneurysms in visceral arteries that may overlap with the spectrum of polyarteritis nodosa (PAN)1,2,3. The Chapel Hill Consensus Conference (CHCC) 2012 defines PAN as a necrotizing vasculitis of medium or small arteries without glomerulonephritis or vasculitis in arterioles, venules, or capillaries and not associated with antineutrophil cytoplasmic antibodies4. Now, with the discovery of DADA2, we know that monogenic disorders may cause a PAN-like vasculopathy. Thus, DADA2 should be classified under the group of “vasculitis with a probable cause” in CHCC 20124. We herein present the characteristics of 6 DADA2 patients and their response to various therapies. Three of our patients had been initially screened at the U.S. National Institutes of Health (NIH) because they had suggestive features for the CECR1 mutations. Subsequently, we screened 17 patients with suggestive features and identified 3 new cases. We have evaluated the course of these patients for a followup of median 8.5 years. All patients were Turkish and were followed in the departments of Rheumatology and Pediatric Rheumatology at Hacettepe University, Ankara, Turkey. Three (patients 2, 3, and 5) had been included in a previous paper2. Peripheral blood samples for DNA extraction were obtained. Sanger sequencing was performed to sequence 10 exons of CECR1 in NIH (n = 3) and Hacettepe University (n = 3). Primer sequences are available in the Appendix. PCR products were directly sequenced using ABI Prism 3130 Automated Sequencer (Applied Biosystems). We defined 6 DADA2 patients from 5 families. The characteristics and treatment of patients … Address correspondence to Dr. S. Ozen, Department of Pediatrics, Division of Rheumatology, Hacettepe University Faculty of Medicine, Ankara 06100, Turkey. E-mail: sezaozen{at}hacettepe.edu.tr

Screening for the fragile X syndrome among mentally retarded males by hair root analysis

A noninvasive antibody test was used to identify male fragile X patients in special education schools, on the basis of the lack of FMRP in hair roots. We studied 300 males with mental retardation of unknown cause attending special schools. Patients were divided into two groups, based on the scores according to a fragile X check list (Group 1 </= 9 points and Group 2 >/= 10 points). Group 2 consists of 51 males and only 5 males in this group showed no FMRP expression in hair roots within the abnormal range (91%). Fragile X diagnosis in these cases was confirmed by DNA analysis. None of the males scoring more than 10 on the check list was diagnosed positive for the fragile X syndrome using DNA analysis. With our antibody test on hair roots we did not detect a fragile X patient in Group 1. The FMRP antibody test on hair roots is suitable in a screening program for the fragile X syndrome among mentally retarded males attending special education schools.