A female with complete lack of Müllerian fusion, postaxial polydactyly, and tetralogy of fallot: Genetic heterogeneity of McKusick-Kaufman syndrome or a unique syndrome?

A rare mutant of OFD1 gene responsible for Joubert syndrome with significant phenotype variation

Joubert syndrome (JBTS), a rare genetic disorder resulted from primary cilium defects or basal-body dysfunction, is characterized by agenesis of cerebellar vermis and abnormal brain stem. Both genotypes and phenotypes of JBTS are highly heterogeneous. The identification of pathogenic gene variation is essential for making a definite diagnosis on JBTS. Here, we found that hypoplasia of cerebellar vermis occurred in three male members in a Chinese family. Then, we performed whole exome sequencing to identify a novel missense mutation c.599T > C (p. L200P) in the OFD1 gene which is the candidate gene of X-linked JBTS (JBST10). The following analysis showed that the variant was absent in the 1000 Genomes, ExAC and the 200 female controls; the position 200 Leucine residue was highly conserved across species; the missense variant was predicted to be deleterious using PolyPhen-2, PROVEAN, SIFT and Mutation Taster. The OFD1 expression was heavily lower in the proband and an induced male fetus compared with a healthy male with a wild-type OFD1 gene. The in vitro expression analysis of transiently transfecting c.599T or c.599C plasmids into HEK-293T cells confirmed that the missense mutation caused OFD1 reduction at the protein level. And further the mutated OFD1 decreased the level of Gli1 protein, a read-out of Sonic hedgehog (SHH) signaling essential for development of central neural system. A known pathogenic variant c.515T > C (p. L172P) showed the similar results. All of these observations suggested that the missense mutation causes the loss function of OFD1, resulting in SHH signaling impairs and brain development abnormality. In addition, the three patients have Dandy-Walker malformation, macrogyria and tetralogy of Fallot, respectively, the latter two of which are firstly found in JBTS10 patients. In conclusion, our findings expand the context of genotype and phenotype in the JBTS10 patients.

McKusick-Kaufman or Bardet-Biedl syndrome? A new borderline case in an Italian nonconsanguineous healthy family

McKusick-Kaufman syndrome (MKS, OMIM #236700) is a rare syndrome inherited in an autosomal recessive pattern with a phenotypic triad comprising hydrometrocolpos (HMC), postaxial polydactyly (PAP), and congenital cardiac disease (CHD). The syndrome is caused by mutations in the MKKS gene mapped onto chromosome 20p12 between D20S162 and D20S894 markers. Mutations in the same gene causes Bardet-Biedl-6 syndrome (BBS-6, OMIM #209900) inherited in an autosomal recessive pattern. BBS-6 comprises retinitis pigmentosa, polydactyly, obesity, mental retardation, renal and genital anomalies. HMC, CHD, and PAP defects can also occur in BBS-6, and there is a significant clinical overlap between MKS and BBS-6 in childhood. We describe a new borderline case of MKS and BBS syndrome and suggest insights for understanding correlation between MKKS gene mutations and clinical phenotype. Here, we report the results of molecular analysis of MKKS in a female proband born in an Italian nonconsanguineous healthy family that presents HMC and PAP. The mutational screening revealed the presence of two different heterozygous missense variants (p.242A>S in exon 3, p.339 I>V in exon 4) in the MKKS gene, and a nucleotide variation in 5’UTR region in exon 2 (-417 A>C).

Recurrent aberrations identified by array-CGH in patients with Mayer-Rokitansky-Küster-Hauser syndrome

OBJECTIVE

To identify genetic causes of Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome.

DESIGN

Prospective laboratory study.

SETTING

University hospital.

PATIENT(S)

Fifty-six patients with MRKH syndrome.

INTERVENTION(S)

Identification of microdeletions and -duplications in a group of 48 MRKH patients by array-CGH. Results obtained by array-CGH were confirmed by RT-qPCR. Sequential analysis of two candidate genes LHX1 and HNF1B in a group of 56 MRKH patients.

MAIN OUTCOME MEASURE(S)

Identification of chromosomal regions and genes (recurrent and private) associated with MRKH syndrome.

RESULT(S)

We could delineate three definitively relevant regions (1q21.1, 17q12, and 22q11.21) and suggest that LHX1 und HNF1B are candidate genes for MRKH syndrome, because we identified recurrent deletions affecting these genes and a possible causative missense mutation in LHX1.

CONCLUSION(S)

Our findings suggest that different chromosomal regions are associated with MRKH syndrome.

Differential changes in TGF-β/BMP signaling pathway in the right ventricular myocardium of newborns with hypoplastic left heart syndrome

BACKGROUND

Hypoplastic left heart syndrome (HLHS) is characterized by underdevelopment of the left ventricle (LV) and increased biomechanical stress on the right ventricle (RV) from single ventricle physiology. Despite the clinical significance, the signaling pathways active during RV remodeling and disease progression are not known. To address this, we examined differential changes in expression of genes associated with transforming growth factor-beta (TGF-beta)/bone morphogenetic protein (BMP) signaling in RV tissue isolated from HLHS patients relative to RV and LV tissue from control subjects.

METHODS AND RESULTS

Quantitative real-time polymerase chain reaction was used to detect changes in expression of 84 genes involved in TGF-beta/BMP-mediated cardiac development, cell growth, and differentiation in RV tissue collected from 6 neonates with HLHS undergoing stage 1 Norwood procedure (age, 1-7 days; mean, 4 days) and RV and LV tissue obtained from 5 infants with noncardiac pathology (age range, 1-135 days: mean, 85 days) that served as controls. Analysis of gene expression profiles between control-LV and control-RV revealed significant depression of TGF-beta/BMP signaling in RV compared with LV. Of the 84 genes analyzed, 38 were differentially expressed between HLHS-RV and control-RV, whereas only 22 compared with control-LV. Significant changes were observed in: tissue remodeling genes including Activin receptor type IIA (ACVR2A) (+2.13) and Activin receptor-like kinase 1 (ACVRL1) (+2.22); and cell survival, growth, and differentiation genes including CDC25A (+2.18), p21 (-3.64), p15 (+2.15), BMP5 (+4.58), BMP3 (+2.16), GDF3 (+8.59), NODAL (+2.32), and BMP binding endothelial regulator (BMPER) (+4.58). The most significant changes common to HLHS-RV versus control-RV and control-LV sample groups is observed for Anti müllerian hormone receptor 2 (AMHR2) (+18.79 control-RV, +3.38 control-LV), and the BMP antagonist Inhibin alpha (INHA) (+11.47 control-RV, +5.73 control-LV).

CONCLUSIONS

Although this descriptive study does not allow cause-effect inferences, our results suggest changes in cardiac development pathways and upregulation of genes associated with cell growth and differentiation in the neonatal RV of children with HLHS. These molecular profiles are more closely related to those observed in the normal LV rather than normal RV at similar maturational age. This work provides the basis for future mechanistic studies to elucidate the molecular mechanisms regulating RV remodeling in HLHS.

Genetic disorders involving molecular-chaperone genes: a perspective

Molecular chaperones are important for maintaining a functional set of proteins in all cellular compartments. Together with protein degradation machineries (e.g., the ubiquitin-proteasome system), chaperones form the core of the cellular protein-quality control mechanism. Chaperones are proteins, and as such, they can be affected by mutations. At least 15 disorders have been identified that are associated with mutations in genes encoding chaperones, or molecules with features suggesting that they function as chaperones. These chaperonopathies and a few other candidates are presented in this article. In most cases, the mechanisms by which the defective genes contribute to the observed phenotypes are still uncharacterized. However, the reported observations definitely point to the possibility that abnormal chaperones participate in pathogenesis. The available data open novel perspectives and should encourage searches for new genetic chaperonopathies, as well as further analyses of the disorders discussed in this article, including detection of new cases.

Mullerian Agenesis and Thrombocytopenia Absent Radius Syndrome: A Case Report and Review of Syndromes Associated With Mullerian Agenesis

Mullerian agenesis, commonly referred to as Mayer-Rokitansky-Kuster-Hauser syndrome (MRKHS), is a congenital defect that is most commonly associated with renal and spinal malformations. It is very rare for Mullerian agenesis to be accompanied by malformations of the extremities. In this report, we describe a 22-year-old woman with Mullerian agenesis and thrombocytopenia absent radius syndrome (TARS). We also review rare syndromes associated with Mullerian anomalies, including Mullerian hypoplasia/aplasia-renal agenesis-cervicothoracic somite dysplasia (MURCS), Roberts syndrome, Bardet-Biedl syndrome (BBS), McKusick-Kaufman syndrome (MKS), Wolf-Hirschhorn syndrome, and others. The pathogenesis of these complex malformation syndromes is not well understood as a result of their sporadic occurrence. However, some of these syndromes do follow a pattern of inheritance, suggesting that they could provide insights into our understanding of their origins.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to review the rare congenital defects associated with Mullerian agenesis, to determine the genetic etiologies of the associated syndromes with Mullerian agenesis, and to discuss information for parental counseling related to inheritance patterns and growth and development of the affected child.