Renata Posmyk

Phenotype and genotype in 103 patients with tricho-rhino-phalangeal syndrome.

Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities, and subdivided in TRPS I, caused by mutations in TRPS1, and TRPS II, caused by a contiguous gene deletion affecting (amongst others) TRPS1 and EXT1. We performed a collaborative international study to delineate phenotype, natural history, variability, and genotype-phenotype correlations in more detail. We gathered information on 103 cytogenetically or molecularly confirmed affected individuals. TRPS I was present in 85 individuals (22 missense mutations, 62 other mutations), TRPS II in 14, and in 5 it remained uncertain whether TRPS1 was partially or completely deleted. Main features defining the facial phenotype include fine and sparse hair, thick and broad eyebrows, especially the medial portion, a broad nasal ridge and tip, underdeveloped nasal alae, and a broad columella. The facial manifestations in patients with TRPS I and TRPS II do not show a significant difference. In the limbs the main findings are short hands and feet, hypermobility, and a tendency for isolated metacarpals and metatarsals to be shortened. Nails of fingers and toes are typically thin and dystrophic. The radiological hallmark are the cone-shaped epiphyses and in TRPS II multiple exostoses. Osteopenia is common in both, as is reduced linear growth, both prenatally and postnatally. Variability for all findings, also within a single family, can be marked. Morbidity mostly concerns joint problems, manifesting in increased or decreased mobility, pain and in a minority an increased fracture rate. The hips can be markedly affected at a (very) young age. Intellectual disability is uncommon in TRPS I and, if present, usually mild. In TRPS II intellectual disability is present in most but not all, and again typically mild to moderate in severity. Missense mutations are located exclusively in exon 6 and 7 of TRPS1. Other mutations are located anywhere in exons 4-7. Whole gene deletions are common but have variable breakpoints. Most of the phenotype in patients with TRPS II is explained by the deletion of TRPS1 and EXT1, but haploinsufficiency of RAD21 is also likely to contribute. Genotype-phenotype studies showed that mutations located in exon 6 may have somewhat more pronounced facial characteristics and more marked shortening of hands and feet compared to mutations located elsewhere in TRPS1, but numbers are too small to allow firm conclusions.

Contribution of RIT1 mutations to the pathogenesis of Noonan syndrome: four new cases and further evidence of heterogeneity.

Noonan syndrome (NS) is a common developmental disorder presenting with dysmorphic craniofacial features, heart defects, and short stature. It belongs to the group of RASopathies caused by germline mutations in genes encoding proteins involved in the RAS/MAPK signaling pathway. Although mutations in nine genes are known to cause NS, approximately 30% of the cases still have unexplained etiology. To identify the new causative genes, 42 patients with a clinical diagnosis of NS, who had negative results on Sanger sequencing of PTPN11, SOS1, and RAF1 (the most common NS genes), were selected for whole exome sequencing. In two patients, mutations in recently described new NS gene—RIT1 were found (c.244T>G [p.Phe82Val] and c.270G>C [p.Met90Ile]). Further analysis of a larger cohort (n = 64) of NS patients with classic Sanger sequencing revealed the presence of RIT1 mutation c.284G>C (p.Gly95Ala) in two additional patients. All the detected mutations were localized in switch II domain responsible for GTPase activity. The modeling of RIT1 protein structure revealed that the mutated amino acids and their interacting residues are evolutionary conserved and any residue replacement might change the structural stability and/or protein internal dynamics influencing catalytic activity of the protein. It seems that the identified mutations might alter protein function and therefore, the activity of ERK and P38 MAPK pathways, thus underlying the specific phenotype observed in NS patients. Our study independently confirms the role of RIT1 in the pathogenesis of Noonan syndrome.

WRN Mutation Update: Mutation Spectrum, Patient Registries, and Translational Prospects

Werner syndrome (WS) is a rare autosomal recessive disorder characterized by a constellation of adult onset phenotypes consistent with an acceleration of intrinsic biological aging. It is caused by pathogenic variants in the WRN gene, which encodes a multifunctional nuclear protein with exonuclease and helicase activities. WRN protein is thought to be involved in optimization of various aspects of DNA metabolism, including DNA repair, recombination, replication, and transcription. In this update, we summarize a total of 83 different WRN mutations, including eight previously unpublished mutations identified by the International Registry of Werner Syndrome (Seattle, WA) and the Japanese Werner Consortium (Chiba, Japan), as well as 75 mutations already reported in the literature. The Seattle International Registry recruits patients from all over the world to investigate genetic causes of a wide variety of progeroid syndromes in order to contribute to the knowledge of basic mechanisms of human aging. Given the unusually high prevalence of WS patients and heterozygous carriers in Japan, the major goal of the Japanese Consortium is to develop effective therapies and to establish management guidelines for WS patients in Japan and elsewhere. This review will also discuss potential translational approaches to this disorder, including those currently under investigation.

L239F founder mutation in GDAP1 is associated with a mild Charcot-Marie-Tooth type 4C4 (CMT4C4) phenotype.

Over 40 mutations in the GDAP1 gene have been shown to segregate with Charcot–Marie–Tooth disease (CMT). Among these, only two mutations, i.e., S194X and Q163X have been reported in a sufficient number of CMT families to allow for the construction of reliable phenotype–genotype correlations. Both the S194X and Q163X mutations have been shown to segregate with an early-onset and severe neuropathy resulting in loss of ambulance at the beginning of the second decade of life. In this study, we identified the L239F mutation in the GDAP1 gene in one Bulgarian and five Polish families. We hypothesized that the L239F mutation may result from a founder effect in the European population since this mutation has previously been reported in Belgian, Czech, and Polish patients. In fact, we detected a common disease-associated haplotype within the 8q13-q21 region in the Polish, German, Italian, Czech, and Bulgarian CMT families. Like the previously detected “regional” S194X and Q163X mutations, respectively present in Maghreb countries and in patients of Spanish descent, the L239F mutation seems to be the most common GDAP1 pathogenic variant in the Central and Eastern European population. Given the likely presence of a common ancestor harboring the L239F mutation, we decided to compare the phenotypes of the CMT (L239F) patients collected in this study with those of previously reported cases. In contrast to CMT4A caused by the S194X and Q163X mutations, the CMT phenotype resulting from the L239F substitution represents a milder clinical entity with a long-preserved period of ambulance at least until the end of the second decade of life.

The smallest de novo deletion of 20q11.21-q11.23 in a girl with feeding problems, retinal dysplasia, and skeletal abnormalities.

We report on a de novo interstitial deletion of 20q11.21–q11.23 in a 2‐year‐old girl with a set of dysmorphic features, cleft palate, heart defect, severe feeding problems, failure to thrive, developmental delay, preaxial polydactyly (right thumb), and retinal dysplasia. Interstitial microdeletions of the long arm of chromosome 20 are rare. Exclusively rare are proximal microdeletions involving 20q11–q12 region. Our patient is the fourth described so far and has the smallest deleted region 20q11.21–q11.23 of 5.7 Mb. The defined clinical phenotype of our patient is very similar to previously published cases and confirms the existence of retinal dysplasia and skeletal abnormalities as a part of phenotypic spectrum for deletion 20q11–q12. Description of four similar patients, including two almost identical, suggests a new distinct, phenotypicaly recognizable microdeletion syndrome associated with the loss of 20q11–q12 region.

New case of Primrose syndrome with mild intellectual disability

We report on a 27‐year‐old man, who represents the sixth and the youngest published case of Primrose syndrome. Primrose syndrome (PS) (OMIM#295090) is an extremely rare entity of unknown etiology characterized by the progressive wasting of distal muscles of the legs, the small muscles of the hands resulting in contractures, the presence of intellectual disability, hearing problems, cataracts, brain calcification, and the ossification of ear cartilage. All the main manifestations were present in our patient. Despite the phenotypic similarity to five other cases, our patient had mild intellectual disability. Additionally we found hypergonadotropic hypogonadism and a low bone density due to progressive osteoporosis. We discuss our observations in relation to previously published cases, and we stress the need for the detail and phenotypic descriptions of further cases as PS remains rare, and the genetic basis is still undiscovered.

Is diagnosing cardio-facio-cutaneous (CFC) syndrome still a challenge? Delineation of the phenotype in 15 Polish patients with proven mutations, including novel mutations in the BRAF gene

Cardio-facio-cutaneous (CFC) syndrome is characterized by a variable degree of developmental delay and congenital anomalies, including characteristic facial, cardiac, and ectodermal abnormalities. It is caused by activating mutations in the Ras/mitogen-activated protein kinase (MAPK) signaling pathway. In, however, approximately 10%-30% of individuals with a clinical diagnosis of CFCS, no mutation of the causative gene is found. Therefore, clinical studies in patients with the CFCS spectrum are valuable. To investigate the phenotypic spectrum and molecular diversity of germline mutations affecting genes encoding serine/threonine kinases, a group of 15 children and young adults with a diagnosis of CFCS was screened. We documented three novel mutations in the BRAF gene and correlated clinical findings with causative mutations in the BRAF or MEK1/MEK2 genes.

Wolf-Hirschhorn syndrome due to pure and translocation forms of monosomy 4p16.1 → pter.

The aim of this study was to obtain a quantitative definition of Wolf–Hirschhorn syndrome (WHS) through systematic phenotypic analyses in a group of six children with 4p15.32 → pter, 4p15.33 → pter, or 4p16.1 → pter monosomy (considered together as M4p16.1). These results were used for evaluation of the phenotypic effects of a double chromosome imbalance in one child with 4p16.1 → pter monosomy and additional 11q23.3 → qter trisomy. Children with pure M4p16.1 presented with a total of 227 clinical and morphological traits, of which 119 were positive in at least two of them. These traits overlap to a great extent with clinical criteria defining the WHS phenotype. Among the 103 traits identified in the child with unbalanced translocation der(4)t(4;11)(p16.1;q23.3), most clinical and developmental traits (but only 11 morphological) were found to be shared by WHS children with pure M4p16.1 and at least one reported patient with pure 11q trisomy. Forty‐six traits of this child corresponded solely to those identified in at least one child with pure M4p16.1. Only five traits of the hybrid phenotype were present in at least one child with pure distal 11q trisomy but in none of the present children with pure M4p16.1. In conclusion, most of the morphological traits of the hybrid phenotype in the child with der(4)t(4;11)(p16.1;q23.3) can be attributed to the M4p16.1, whereas their overlap with those associated with pure distal 11q trisomy is less evident. Phenotype analyses based on the same systematic data acquisition may be useful in understanding the phenotypic effects of different chromosome regions in complex rearrangements.

Expression of the energy substrate transporters in uterine fibroids.

Proliferating cells exhibit accelerated rates of substrate utilization, favoring glucose over fatty acids (FAs) oxidation. Protein-mediated transport is thought to play a predominant role in facilitating either glucose or FA routing into the cells. In the present study, we examined the expression of glucose transporters (GLUT-1, GLUT-4) and fatty acids transporters (FAT/CD36, FATP-1, FATP-4) at transcript and protein levels as well as cytosolic fatty acid binding proteins (H-FABP, ACBP) in human fibroids (n=74, size up to 3cm diameter) and compared with pair-matched healthy myometrium. Additionally lipid content (diacylglycerols, triacylglycerols and ceramide) was estimated by gas liquid chromatography (GLC). Uterine fibroids displayed decreased expression of both FAT/CD36 and FATP-1 proteins along with lower diacylglycerol (DAG) and triacylglycerol (TAG) content as compared to healthy pair-matched myometrium. The expression of glucose transport proteins (GLUT-4 and GLUT-1) remained relatively constant, although the higher expression of GLUT-1 in uterine fibroids did not reach the minimum significance threshold (p=0.056). However, no change in either cytochrome c oxidase (COX IV) or hydroxyacyl-CoA dehydrogenase (HADHSC) was observed and these data confirm a possible metabolic shift favoring glucose utilization over fatty acid oxidation in human uterine fibroids.

The Tatton-Brown-Rahman Syndrome: A clinical study of 55 individuals with de novo constitutive DNMT3A variants

Tatton-Brown-Rahman syndrome (TBRS; OMIM 615879), also known as the DNMT3A-overgrowth syndrome, is an overgrowth intellectual disability syndrome first described in 2014 with a report of 13 individuals with constitutive heterozygous DNMT3A variants. Here we have undertaken a detailed clinical study of 55 individuals with de novo DNMT3A variants, including the 13 previously reported individuals. An intellectual disability and overgrowth were reported in >80% of individuals with TBRS and were designated major clinical associations. Additional frequent clinical associations (reported in 20-80% individuals) included an evolving facial appearance with low-set, heavy, horizontal eyebrows and prominent upper central incisors; joint hypermobility (74%); obesity (weight ³2SD, 67%); hypotonia (54%); behavioural/psychiatric issues (most frequently autistic spectrum disorder, 51%); kyphoscoliosis (33%) and afebrile seizures (22%). One individual was diagnosed with acute myeloid leukaemia in teenage years. Based upon the results from this study, we present our current management for individuals with TBRS