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RUNX2 (Runt-related transcription factor 2) is a master regulator of osteoblast differentiation, cartilage and bone development. Pathogenic variants in RUNX2 have been linked to the Cleidocranial dysplasia (CCD), which is characterized by hypoplasia or aplasia of clavicles, delayed fontanelle closure, and dental anomalies. Here, we report 11 unrelated Polish patients with CCD caused by pathogenic alterations located in the Runt domain of RUNX2. In total, we identified eight different intragenic variants, including seven missense and one splicing mutation. Three of them are novel: c.407T>A p.(Leu136Gln), c.480C>G p.(Asn160Lys), c.659C>G p.(Thr220Arg), additional three were not functionally tested: c.391C>T p.(Arg131Cys), c.580+1G>T p.(Lys195_Arg229del), c.652A>G p.(Lys218Glu), and the remaining two: c.568C>T p.(Arg190Trp), c.673C>T p.(Arg225Trp) were previously reported and characterized. The performed transactivation and localization studies provide evidence of decreased transcriptional activity of RUNX2 due to mutations targeting the Runt domain and prove that impairment of nuclear localization signal (NLS) affects the subcellular localization of the protein. Presented data show that pathogenic variants discovered in our patients have a detrimental effect on RUNX2, triggering the CCD phenotype.

Cornelia de Lange syndrome (CdLS) is a clinically heterogeneous disorder characterized by typical facial dysmorphism, cognitive impairment and multiple congenital anomalies. Approximately 75% of patients carry a variant in one of the five cohesin-related genes NIPBL, SMC1A, SMC3, RAD21 and HDAC8. Herein we report on the clinical and molecular characterization of 11 patients carrying 10 distinct variants in HDAC8. Given the high number of variants identified so far, we advise sequencing of HDAC8 as an indispensable part of the routine molecular diagnostic for patients with CdLS or CdLS-overlapping features. The phenotype of our patients is very broad, whereas males tend to be more severely affected than females, who instead often present with less canonical CdLS features. The extensive clinical variability observed in the heterozygous females might be at least partially associated with a completely skewed X-inactivation, observed in seven out of eight female patients. Our cohort also includes two affected siblings whose unaffected mother was found to be mosaic for the causative mutation inherited to both affected children. This further supports the urgent need for an integration of highly sensitive sequencing technology to allow an appropriate molecular diagnostic, genetic counseling and risk prediction.

Multiple epiphyseal dysplasia (MED) is an autosomal dominantly inherited chondrodysplasia. It is clinically highly heterogeneous, partially because of its complex genetic background. Mutations in four genes, COL9A2, COL9A3, COMP, and MATR3, all coding for cartilage extracellular matrix components (i.e., the alpha2 and alpha 3 chains of collagen IX, cartilage oligomeric matrix protein, and matrilin-3), have been identified in this disease so far, but no mutations have yet been reported in the third collagen IX gene, COL9A1, which codes for the alpha1(IX) chain. MED with apparently recessive inheritance has been reported in some families. A homozygous R279W mutation was recently found in the diastrophic dysplasia sulfate transporter gene, DTDST, in a patient with MED who had a club foot and double-layered patella. The series consisted of 41 probands with MED, 16 of whom were familial and on 4 of whom linkage analyses were performed. Recombination was observed between COL9A1, COL9A2, COL9A3, and COMP and the MED phenotype in two of the families, and between COL9A2, COL9A3, and COMP and the phenotype in the other two families. Screening of COL9A1 for mutations in the two probands from the families in which this gene was not involved in the recombinations failed to identify any disease-causing mutations. The remaining 37 probands were screened for mutations in all three collagen IX genes and in the COMP gene. The probands with talipes deformities or multipartite patella were also screened for the R279W mutation in DTDST. The analysis resulted in identification of three mutations in COMP and one in COL9A1, but none in the other two collagen IX genes. Two of the probands with a multipartite patella had the homozygous DTDST mutation. The results show that mutations in COL9A1 can cause MED, but they also suggest that mutations in COL9A1, COL9A2, COL9A3, COMP, and DTDST are not the major causes of MED and that there exists at least one additional locus.

Background Metacarpal 4–5 fusion (MF4; MIM %309630) is a rare congenital malformation of the hand characterised by the partial or complete fusion of the fourth and fifth metacarpals. The anomaly occurs as an isolated trait or part of a genetic syndrome. Methods To search for disease-causing mutation, whole exome sequencing (WES) was performed on samples from a single trio. Before WES, molecular screening including gene sequencing and array comparative genomic hybridisation was applied. Validation of WES and segregation studies were done using routine Sanger sequencing. Results Exome sequencing detected a nonsense mutation (c.C535T; p.R179X) in exon 3 of the FGF16 gene, which maps to chromosome Xq21.1. Mutational screening of the FGF16 gene performed in an unrelated proband of different ethnicity showed another nonsense mutation in exon 3 (c.C470A; p.S157X). Conclusions This study shows that truncating mutations of FGF16 are associated with X-linked recessive metacarpal 4–5 fusion. The study provides evidence for the involvement of FGF16 in the fine tuning of the human skeleton of the hand.

Background The Nanos gene is a key translational regulator of specific mRNAs involved in Drosophila germ cell development. Disruption of mammalian homologues, Nanos2 or Nanos3 , causes male infertility in mice. In humans, however, no evidence of NANOS2 or NANOS3 mutations causing male infertility has been reported. Although Nanos1 seems dispensable for mouse reproduction, we sought to analyse for the first time its homologue in infertile men. Methods A group of 195 patients manifesting non-obstructive azoospermia or oligozoospermia were tested for mutations of the NANOS1 gene, using single-strand conformation polymorphism and DNA sequencing. Results Three types of NANOS1 gene mutations were identified in five patients and were absent in 800 chromosomes of fertile men. Pedigree analysis indicated a dominant inheritance pattern with penetration limited to males. Two mutations caused deletions of single amino acids, p.Pro77_Ser78delinsPro and p.Ala173del, each of them identified in two unrelated patients. Both types of deletions were located in the NANOS1 N-terminus (responsible for protein interactions) and were associated with a lack of germ cells in testes. Interestingly, the Pro77_Ser78delinsPro mutation altered interaction of NANOS1 with a microRNA biogenesis factor, GEMIN3. The third identified mutation, p.[(Arg246His; Arg276Tyr)], found in the C-terminal RNA-binding domain, was present in a single oligo-astheno-teratozoospermic man. We bioinformatically demonstrated that the p.Arg246His substitution causes a decrease in the positive charge of this domain, potentially altering RNA-binding. Conclusions This is the first report describing the association of NANOS1 gene mutations with human infertility. Two different infertility phenotypes may reflect distinct functions of N-terminal versus C-terminal regions of NANOS1.

Background The 22q11.2 microdeletion syndrome (22q11.2 deletion syndrome -22q11.2DS) refers to congenital abnormalities, including primarily heart defects and facial dysmorphy, thymic hypoplasia, cleft palate and hypocalcaemia. Microdeletion within chromosomal region 22q11.2 constitutes the molecular basis of this syndrome. The 22q11.2 microdeletion syndrome occurs in 1/4000 births. The aim of this study was to determine the frequency of 22q11.2 microdeletion in 87 children suffering from a congenital heart defect (conotruncal or non-conotruncal) coexisting with at least one additional 22q11.2DS feature and to carry out 22q11.2 microdeletion testing of the deleted children's parents. We also attempted to identify the most frequent heart defects in both groups and phenotypic traits of patients with microdeletion to determine selection criteria for at risk patients. Methods The analysis of microdeletions was conducted using fluorescence in situ hybridization (FISH) on metaphase chromosomes and interphase nuclei isolated from venous peripheral blood cultures. A molecular probe (Tuple) specific to the HIRA (TUPLE1, DGCR1) region at 22q11 was used for the hybridisation. Results Microdeletions of 22q11.2 region were detected in 13 children with a congenital heart defect (14.94% of the examined group). Microdeletion of 22q11.2 occurred in 20% and 11.54% of the conotruncal and non-conotruncal groups respectively. Tetralogy of Fallot was the most frequent heart defect in the first group of children with 22q11.2 microdeletion, while ventricular septal defect and atrial septal defect/ventricular septal defect were most frequent in the second group. The microdeletion was also detected in one of the parents of the deleted child (6.25%) without congenital heart defect, but with slight dysmorphism. In the remaining children, 22q11.2 microdeletion originated de novo. Conclusions Patients with 22q11.2DS exhibit wide spectrum of phenotypic characteristics, ranging from discreet to quite strong. The deletion was inherited by one child. Our study suggests that screening for 22q11.2 microdeletion should be performed in children with conotruncal and non-conotruncal heart defects and with at least one typical feature of 22q11.2DS as well as in the deleted children's parents.