A defect in the inner kinetochore protein CENPT causes a new syndrome of severe growth failure.

Primordial growth failure has been linked to defects in the biology of cell division and replication. The complex processes involved in microtubule spindle formation, organization and function have emerged as a dominant patho-mechanism in these conditions. The majority of reported disease genes encode for centrosome and centriole proteins, leaving kinetochore proteins by which the spindle apparatus interacts with the chromosomes largely unaccounted for. We report a novel disease gene encoding the constitutive inner kinetochore member CENPT, which is involved in kinetochore targeting and assembly, resulting in severe growth failure in two siblings of a consanguineous family. We herein present studies on the molecular and cellular mechanisms that explain how genetic mutations in this gene lead to primordial growth failure. In both, affected human cell lines and a zebrafish knock-down model of Cenpt, we observed aberrations in cell division with abnormal accumulation of micronuclei and of nuclei with increased DNA content arising from incomplete and/or irregular chromosomal segregation. Our studies underscore the critical importance of kinetochore function for overall body growth and provide new insight into the cellular mechanisms implicated in the spectrum of these severe growth disorders.

Mutations in Epigenetic Regulation Genes Are a Major Cause of Overgrowth with Intellectual Disability.

To explore the genetic architecture of human overgrowth syndromes and human growth control, we performed experimental and bioinformatic analyses of 710 individuals with overgrowth (height and/or head circumference ≥+2 SD) and intellectual disability (OGID). We identified a causal mutation in 1 of 14 genes in 50% (353/710). This includes HIST1H1E, encoding histone H1.4, which has not been associated with a developmental disorder previously. The pathogenic HIST1H1E mutations are predicted to result in a product that is less effective in neutralizing negatively charged linker DNA because it has a reduced net charge, and in DNA binding and protein-protein interactions because key residues are truncated. Functional network analyses demonstrated that epigenetic regulation is a prominent biological process dysregulated in individuals with OGID. Mutations in six epigenetic regulation genes-NSD1, EZH2, DNMT3A, CHD8, HIST1H1E, and EED-accounted for 44% of individuals (311/710). There was significant overlap between the 14 genes involved in OGID and 611 genes in regions identified in GWASs to be associated with height (p = 6.84 × 10-8), suggesting that a common variation impacting function of genes involved in OGID influences height at a population level. Increased cellular growth is a hallmark of cancer and there was striking overlap between the genes involved in OGID and 260 somatically mutated cancer driver genes (p = 1.75 × 10-14). However, the mutation spectra of genes involved in OGID and cancer differ, suggesting complex genotype-phenotype relationships. These data reveal insights into the genetic control of human growth and demonstrate that exome sequencing in OGID has a high diagnostic yield.

Mutations in chromatin regulators functionally link Cornelia de Lange syndrome and clinically overlapping phenotypes.

The coordinated tissue-specific regulation of gene expression is essential for the proper development of all organisms. Mutations in multiple transcriptional regulators cause a group of neurodevelopmental disorders termed "transcriptomopathies" that share core phenotypical features including growth retardation, developmental delay, intellectual disability and facial dysmorphism. Cornelia de Lange syndrome (CdLS) belongs to this class of disorders and is caused by mutations in different subunits or regulators of the cohesin complex. Herein, we report on the clinical and molecular characterization of seven patients with features overlapping with CdLS who were found to carry mutations in chromatin regulators previously associated to other neurodevelopmental disorders that are frequently considered in the differential diagnosis of CdLS. The identified mutations affect the methyltransferase-encoding genes KMT2A and SETD5 and different subunits of the SWI/SNF chromatin-remodeling complex. Complementary to this, a patient with Coffin-Siris syndrome was found to carry a missense substitution in NIPBL. Our findings indicate that mutations in a variety of chromatin-associated factors result in overlapping clinical phenotypes, underscoring the genetic heterogeneity that should be considered when assessing the clinical and molecular diagnosis of neurodevelopmental syndromes. It is clear that emerging molecular mechanisms of chromatin dysregulation are central to understanding the pathogenesis of these clinically overlapping genetic disorders.

Bainbridge-Ropers syndrome caused by loss-of-function variants in ASXL3: a recognizable condition.

Truncating ASXL3 mutations were first identified in 2013 by Bainbridge et al. as a cause of syndromic intellectual disability in four children with similar phenotypes using whole-exome sequencing. The clinical features - postulated by Bainbridge et al. to be overlapping with Bohring-Opitz syndrome - were developmental delay, severe feeding difficulties, failure to thrive and neurological abnormalities. This condition was included in OMIM as 'Bainbridge-Ropers syndrome' (BRPS, #615485). To date, a total of nine individuals with BRPS have been published in the literature in four reports (Bainbridge et al., Dinwiddie et al, Srivastava et al. and Hori et al.). In this report, we describe six unrelated patients with newly diagnosed heterozygous de novo loss-of-function variants in ASXL3 and concordant clinical features: severe muscular hypotonia with feeding difficulties in infancy, significant motor delay, profound speech impairment, intellectual disability and a characteristic craniofacial phenotype (long face, arched eyebrows with mild synophrys, downslanting palpebral fissures, prominent columella, small alae nasi, high, narrow palate and relatively little facial expression). The majority of key features characteristic for Bohring-Opitz syndrome were absent in our patients (eg, the typical posture of arms, intrauterine growth retardation, microcephaly, trigonocephaly, typical facial gestalt with nevus flammeus of the forehead and exophthalmos). Therefore we emphasize that BRPS syndrome, caused by ASXL3 loss-of-function variants, is a clinically distinct intellectual disability syndrome with a recognizable phenotype distinguishable from that of Bohring-Opitz syndrome.

Clinical, cytogenetic, and molecular findings in a patient with a 46,XX,del(18)(q22)/46,XX,idic(18)(q22) karyotype.

Pseudoisodicentric or asymmetrical dicentric chromosomes 18 are rare findings in clinical cytogenetics. So far, only 8 patients with breakpoints in 18q have been reported and in none of them breakpoints were narrowed down to the molecular level. Here, we describe a 17 months old girl with a perimembranous ventricular septal defect, cleft palate, and minor dysmorphism including hypertelorism, flat nose, frontal bossing and low set ears as well as mosaicism for a cell line with a pseudoisodicentric chromosome 18q and a second cell line with a terminal deletion of 11 Mb in 18q22.2→qter. SNP-array investigation revealed a symmetric breakpoint in 18q22.2 and most likely postzygotic formation from the maternal chromosome 18. Clinical findings in all patients reported so far as well as in the patient presented here were in part overlapping with the clinical phenotypes of trisomy 18 and partial monosomy 18q.

ADAMTSL4-associated isolated ectopia lentis: Further patients, novel mutations and a detailed phenotype description.

ADAMTSL4 mutations seem to be the most common cause of isolated ectoplia lentis (EL) and thus are important concerning the differential diagnosis of connective tissue syndromes with EL as main feature. In this study, we describe an additional cohort of patients with apparently isolated EL. All underwent a detailed clinical exam with cardiac evaluation combined with ADAMTSL4 mutation analysis. Mutations were identified in 12/15 patients with EL. Besides the European founder mutation p. (Gln256Profs*38) we identified five further mutations not yet described in the literature: p. (Leu249Tyrfs*21), p. (Ala388Glyfs*8), p. (Arg746His), p. (Gly592Ser), and p. (Arg865His). Clinical evaluation showed common additional ocular features such as high myopia, but no major systemic findings. In particular: no dilatation of the aortic root was reported on. This report increases the total number of patients with ADAMTSL4 mutations reported on today and reviews in detail the clinical findings in all patients reported on to date demonstrate, that these patients have a mainly ocular phenotype. There are no consistent systemic findings. The differentiation between syndromic and isolated EL is crucial for the further surveillance, treatment, and counseling of these patients, especially in young children.

Cutaneous manifestations in trisomy 13 mosaicism: A rare case and review of the literature.

Trisomy 13 mosaicism is a rare genetic disorder affecting a small minority of all trisomy 13 cases. It occurs when two cell populations that are karyotypically different are present in the same individual and are derived from a single zygote. As a rule, the phenotype is mitigated to a less dysmorphic appearance and longer survival, making genetic counseling a difficult task. Capillary hemangiomas are a common feature of full trisomy 13, seen in 27-56% of all cases. We report on an 18-months-old girl with extensive cutaneous anomalies, mild dysmorphic features, and slight psychomotor delay, without structural defects and provide an up-to-date review of all cases of trisomy 13 mosaicism with skin involvement. To our knowledge, this is the second clinical report of a patient with trisomy 13 mosaicism with hemangiomas and port wine stains, but no structural defects. © 2015 Wiley Periodicals, Inc.

Females with de novo aberrations in PHF6: clinical overlap of Borjeson-Forssman-Lehmann with Coffin-Siris syndrome.

Recently, de novo aberrations in PHF6 were identified in females with intellectual disability and with a distinct phenotype including a characteristic facial gestalt with bitemporal narrowing, prominent supraorbital ridges, synophrys, a short nose and dental anomalies, tapering fingers with brachytelephalangy, clinodactyly and hypoplastic nails, short toes with hypoplastic nails, and linear skin hyperpigmentation. In adolescent or older patients, this phenotype overlaps but is not identical with Borjeson-Forssman-Lehmann syndrome in males, caused by X-linked recessive mutations in PHF6. In younger girls there seems to be a striking phenotypic overlap with Coffin-Siris syndrome, which is characterized by intellectual disability, sparse hair and hypoplastic nails. This review will summarize and characterize the female phenotype caused by de novo aberrations in PHF6 and will discuss the overlapping and distinguishing features with Coffin-Siris syndrome.

A newly discovered TSHR variant (L665F) associated with nonautoimmune hyperthyroidism in an Austrian family induces constitutive TSHR activation by steric repulsion between TM1 and TM7.

OBJECTIVE: New in vivo mutations in G protein-coupled receptors open opportunities for insights into the mechanism of receptor activation. Here we describe the molecular mechanism of constitutive TSH receptor (TSHR) activation in an Austrian family with three generations of familial nonautoimmune hyperthyroidism. PATIENTS: The index patient was diagnosed with hyperthyroidism during her first pregnancy. Her first two children were diagnosed with hyperthyroidism at the age of 11 and 10 years, respectively. TSH suppression was also observed in the third child at the age of 8 years, who has normal free T4 levels until now. TSH suppression in infancy was observed in the fourth child. The mother of the index patient was diagnosed with toxic multinodular goiter at the age of 36 years. METHODS: DNA was extracted from blood samples from the index patient, her mother, and her four children. Screening for TSHR mutations was performed by high-resolution melting assays and subsequent sequencing. Elucidation of the underlying mechanism of TSHR activation was carried out by generation and structural analysis of TSHR transmembrane homology models and verification of model predictions by functional characterization of receptor mutations. RESULTS AND CONCLUSIONS: A newly discovered TSHR mutation L665F in transmembrane helix 7 of the receptor was detected in six members of this family. Functional characterization of L665F revealed constitutive activation for the Gs pathway and thus represents the molecular cause for hyperthyroidism in this family. The constitutive activation is possibly linked to a steric clash introduced by the L665F mutation between transmembrane helices 1 and 7.

Single-nucleotide polymorphism array-based characterization of ring chromosome 18.

OBJECTIVE: To study genotype-phenotype correlation of ring chromosome 18 [r(18)] in 9 patients with 46,XN karyotype. STUDY DESIGN: In 9 patients with a de novo 46,XN,r(18) karyotype (7 females, 2 males), we performed high-resolution single-nucleotide polymorphism array analysis (Illumina Human Omni1-QuadV1 array in 6 patients, Affymetrix 6.0 array in 3 patients), investigation of parental origin, and genotype-phenotype correlation. RESULTS: No breakpoint was recurrent. Single metaphases with loss of the ring, double rings, or secondarily rearranged rings were found in some cases, but true mosaicism was present in none of these cases. In 3 patients, additional duplications in 18p (of 1.4 Mb, 2 Mb, and 5.8 Mb) were detected. In 1 patient, an additional deletion of 472 kb in Xp22.33, including the SHOX gene, was found. Parental origin of r(18) was maternal in 2 patients and paternal in 4 patients, and formation was most likely meiotic. Karyotype was normal in all investigated parents (n = 15). At birth, mean maternal age was 30 years (n = 9) and mean paternal age was 34.4 years (n = 9). CONCLUSION: Genotype-phenotype correlation revealed extensive clinical variability but no characteristic r(18) phenotype. Severity of clinical signs were generally correlated with the size of the deletion. Patients with large deletions in 18p and small deletions in 18q exhibited mainly symptoms related to 18p-, whereas those with large deletions in 18q and small deletions in 18p had symptoms of 18q-.

Metopic and sagittal synostosis in Greig cephalopolysyndactyly syndrome: five cases with intragenic mutations or complete deletions of GLI3.

Greig cephalopolysyndactyly syndrome (GCPS) is a multiple congenital malformation characterised by limb and craniofacial anomalies, caused by heterozygous mutation or deletion of GLI3. We report four boys and a girl who were presented with trigonocephaly due to metopic synostosis, in association with pre- and post-axial polydactyly and cutaneous syndactyly of hands and feet. Two cases had additional sagittal synostosis. None had a family history of similar features. In all five children, the diagnosis of GCPS was confirmed by molecular analysis of GLI3 (two had intragenic mutations and three had complete gene deletions detected on array comparative genomic hybridisation), thus highlighting the importance of trigonocephaly or overt metopic or sagittal synostosis as a distinct presenting feature of GCPS. These observations confirm and extend a recently proposed association of intragenic GLI3 mutations with metopic synostosis; moreover, the three individuals with complete deletion of GLI3 were previously considered to have Carpenter syndrome, highlighting an important source of diagnostic confusion.

Hepatoblastoma in a 4-year-old girl with Fanconi anaemia.

CASE REPORT: Hepatoblastoma was diagnosed in a 4-year-old girl receiving growth hormone substitution therapy for short stature. Owing to multiple congenital malformations, VACTERL-H (vertebral, anal, cardiac, tracheal, renal and limb anomalies with hydrocephalus) association had been suggested. Elevated chromosomal breakage rates and G2 phase arrest induced by DNA-crosslinking agents in cellular assays confirmed the diagnosis of Fanconi anaemia (FA), a tumour susceptibility syndrome known to be associated with hepatocellular carcinoma following androgen therapy. Subsequent genotyping revealed biallelic mutations in the FANCD1/BRCA2 gene. CONCLUSION: We describe the first case of hepatoblastoma in a patient with FA to raise awareness of this tumour type in the close clinical observation of early cancer-prone forms of this condition, particularly in the presence of FANCD1/BRCA2 mutations. The present case also underscores the importance of FA testing in patients with VACTERL(-H).

Common and recurrent HPGD mutations in Caucasian individuals with primary hypertrophic osteoarthropathy.

OBJECTIVE: Homozygous recessive germline mutations of the 15-hydroxyprostaglandin dehydrogenase (HPGD) gene, encoding 15-hydroxyprostaglandin dehydrogenase, result in persistent elevation of circulating PGE(2) levels, causing the syndrome of primary hypertrophic osteoarthropathy (PHO). Homozygous HPGD mutations have so far been reported in 10 families, all but one displaying parental consanguinity. Only two of these families were of European origin. We wished to determine the role of HPGD in causing PHO in non-consanguineous European families. METHODS: Five previously unreported families of Caucasian European origin, with one or more individuals affected with typical PHO, were characterized clinically and by complete sequencing of the HPGD coding exons. RESULTS: Biallelic HPGD mutations were identified in affected individuals in all the five families, confirming a very specific association of this phenotype with HPGD mutations. The previously described c.175_176delCT frameshift mutation was observed in association with two different alleles of an adjacent single nucleotide polymorphism. CONCLUSIONS: Biallelic HPGD mutations are found in the majority of patients with typical PHO, and sequencing of the HPGD gene is a highly specific first-line investigation for patients presenting in this way, particularly during childhood. The c.175_176delCT frameshift mutation appears to be recurrent and to be the commonest HPGD mutation in Caucasian families.

Histology and synchrotron radiation-based microtomography of the inner ear in a molecularly confirmed case of CHARGE syndrome.

CHARGE (Coloboma of the iris or retina, heart defects, atresia of the choanae, retardation of growth and/or development, genital anomalies, ear anomalies) syndrome (OMIM #214800) affects about 1 in 10,000 children and is most often caused by chromodomain helicase DNA-binding protein-7 (CHD7) mutations. Inner ear defects and vestibular abnormalities are particularly common. Specifically, semicircular canal (SCC) hypoplasia/aplasia and the presence of a Mondini malformation can be considered pathognomonic in the context of congenital malformations of the CHARGE syndrome. We obtained a temporal bone (TB) of a patient with CHARGE syndrome who died from bacteremia at 3 months of age. The clinical diagnosis was confirmed in the patient by direct DNA sequencing and the detection of a de novo, truncating CHD7 mutation, c.6169dup (p.R2057fs). We assessed changes of the TB and the degree of neural preservation, which may influence the potential benefit of cochlear implantation. The TB was analyzed using synchrotron radiation-based micro computed tomography, and by light microscopy. The vestibular partition consisted of a rudimentary vestibule with agenesis of the SCCs. The cochlea was hypoplastic with poor or deficient interscaling and shortened (Mondini dysplasia). The organ of Corti had near normal structure and innervation. Modiolus and Rosenthal's canal were hypoplastic with perikarya displaced along the axon bundles into the internal acoustic meatus, which may be explained by the arrest or limited migration and translocation of the cell nuclei into the cochlear tube during development.

Long-term follow-up of patients with congenital hyperinsulinism in Austria.

AIM: To assess the neurological and clinical long-term outcome of patients diagnosed with congenital hyperinsulinism (CHI) in Austria. PATIENTS AND METHODS: Fourteen patients diagnosed with CHI (1978-2000) were investigated retrospectively by reviewing hospital records. Thirteen of them were evaluated with either a questionnaire or clinical, neurological and biochemical investigations (age at evaluation 4.2-25.5 years) in a follow-up study in the year 2004. RESULTS: Fifty percent of the patients needed a pancreatectomy. The prevalence of mental retardation was 31%, of epilepsy 15% and of pancreatic insufficiency 14%. None of our patients had developed diabetes mellitus. Additionally the prevalence of obesity was 43% in patients after pancreatectomy. Sixty-nine percent of the patients had no further treatment at the time of follow-up. CONCLUSION: Despite early diagnosis and intensive treatment, 31% of the patients presented with mental retardation.

The changing phenotype in diploid/triploid mosaicism may mimic genetic syndromes with aberrant genomic imprinting: follow up in a 14-year-old girl.

Diploid/triploid mosaicism is a rare chromosome aberration characterized by growth and mental retardation, muscular hypotonia, clinodactyly, syndactyly of fingers and toes, asymmetry of the body and the face, truncal obesity, and pigmentary anomalies of the skin. Many patients initially present with severe growth retardation and develop truncal obesity later in life. Variable phenotype expression during development and restriction of triploid cells to certain tissues explain why the diagnosis of diploid/triploid mosaicism is often delayed. Here, we report on a moderately retarded 14-year-old girl with diploid/triploid mosaicism due to inclusion of the second polar body, whose changing phenotype overlaps considerably with different genetic disorders associated with aberrant genomic imprinting. The observation that triploid cells, which in our patient show remarkably variable distribution in different tissues, may also be present in easily accessible tissues such as urinary sediment or buccal smear may contribute to an earlier diagnosis of this rare syndrome.

Clinical and mutational spectrum of Mowat-Wilson syndrome.

Mowat-Wilson Syndrome is a recently delineated mental retardation syndrome usually associated with multiple malformations and a recognizable facial phenotype caused by defects of the transcriptional repressor ZFHX1B. To address the question of clinical and mutational variability, we analysed a large number of patients with suspected Mowat-Wilson Syndrome (MWS). Without prior knowledge of their mutational status, 70 patients were classified into "typical MWS", "ambiguous" and "atypical" groups according to their facial phenotype. Using FISH, qPCR and sequencing, ZFHX1B deletions, splice site or truncating mutations were detected in all 28 patients classified as typical MWS. No ZFHX1B defect was apparent in the remaining 15 cases with ambiguous facial features or in the 27 atypical patients. Genotype-phenotype analysis confirmed that ZFHX1B deletions and stop mutations result in a recognizable facial dysmorphism with associated severe mental retardation and variable malformations such as Hirschsprung disease and congenital heart defects. Our findings indicate that structural eye anomalies such as microphthalmia should be considered as part of the MWS spectrum. We also show that agenesis of the corpus callosum and urogenital anomalies (especially hypospadias) are significant positive predictors of a ZFHX1B defect. Based on our observation of affected siblings and the number of MWS cases previously reported, we suggest a recurrence risk of around 1%. The lack of missense mutations in MWS and MWS-like patients suggests there may be other, as yet unrecognized phenotypes, associated with missense mutations of this transcription factor.

GJB2 mutations in keratitis-ichthyosis-deafness syndrome including its fatal form.

Keratitis-ichthyosis-deafness syndrome (KID; MIM 148210) is a rare congenital disorder characterized by vascularizing keratitis, sensorineural hearing loss (HL), and progressive erythrokeratoderma. Clinical variability including a fatal course of KID in the first year of life has been reported. Germline missense mutations in GJB2, encoding connexin-26, were recently found to cause KID in 14 unrelated juvenile and adult patients. We identified a de novo GJB2 mutation G45E in a patient displaying the fatal form of the disease. No mutations were detected in five other connexin and mitochondrial genes. The G45E mutation was not reported previously in Caucasian patients but was the third most common GJB2 mutation (16% of disease alleles) in Japanese patients with autosomal recessive non-syndromic HL. This finding suggests different modes of action of the same GJB2 mutation depending on the genetic background. This hypothesis was further substantiated by our observation of a variable clinical course in unrelated KID patients from Austria harboring the common D50N mutation in GJB2.