Ventricular septal defects (VSDs) are recognized as one of the commonest congenital heart diseases (CHD), accounting for up to 40% of all cardiac malformations, and occur as isolated CHDs as well as together with other cardiac and extracardiac congenital malformations in individual patients and families. The genetic etiology of VSD is complex and extraordinarily heterogeneous. Chromosomal abnormalities such as aneuploidy and structural variations as well as rare point mutations in various genes have been reported to be associated with this cardiac defect. This includes both well-defined syndromes with known genetic cause (e.g., DiGeorge syndrome and Holt-Oram syndrome) and so far undefined syndromic forms characterized by unspecific symptoms. Mutations in genes encoding cardiac transcription factors (e.g., NKX2-5 and GATA4) and signaling molecules (e.g., CFC1) have been most frequently found in VSD cases. Moreover, new high-resolution methods such as comparative genomic hybridization enabled the discovery of a high number of different copy number variations, leading to gain or loss of chromosomal regions often containing multiple genes, in patients with VSD. In this chapter, we will describe the broad genetic heterogeneity observed in VSD patients considering recent advances in this field.

WNT signaling, essential for many aspects of development, is among the most commonly altered pathways associated with human disease. While initially studied in cancer, dysregulation of WNT signaling has been determined to be essential for skeletal development and the maintenance of bone health throughout life. In this review, we discuss the role of Wnt signaling in bone development and disease with a particular focus on two areas. First, we discuss the roles of WNT signaling pathways in skeletal development, with an emphasis on congenital and idiopathic skeletal syndromes and diseases that are associated with genetic variations in WNT signaling components. Next, we cover a topic that has long been an interest of our laboratory, how high and low levels of WNT signaling affects the establishment and maintenance of healthy bone mass. We conclude with a discussion of the status of WNT-based therapeutics in the treatment of skeletal disease.

Deciphering non-canonical WNT signaling has proven to be both fascinating and challenging. Discovered almost 30 years ago, non-canonical WNT ligands signal independently of the transcriptional co-activator β-catenin to regulate a wide range of morphogenetic processes during development. The molecular and cellular mechanisms that underlie non-canonical WNT function, however, remain nebulous. Recent results from various model systems have converged to define a core non-canonical WNT pathway consisting of the prototypic non-canonical WNT ligand, WNT5A, the receptor tyrosine kinase ROR, the seven transmembrane receptor Frizzled and the cytoplasmic scaffold protein Dishevelled. Importantly, mutations in each of these signaling components cause Robinow syndrome, a congenital disorder characterized by profound tissue morphogenetic abnormalities. Moreover, dysregulation of the pathway has also been linked to cancer metastasis. As new knowledge concerning the WNT5A-ROR pathway continues to grow, modeling these mutations will likely provide crucial insights into both the physiological regulation of the pathway and the etiology of WNT5A-ROR-driven diseases.

Robinow syndrome is a rare disease with short stature, characteristic phenotypical abnormalities, and intellectual integrity in most cases.
We present the case of a 13-year and one-month-old male who came for medical consultation at 3 years of age due to short stature. Additionally, the patient showed craniofacial dysmorphia, congenital heart disease, and growth hormone deficiency. As per family history, the mother presented the same phenotype. The genetic study identified an unreported variant of the WNT5A gene.
The patient initiated growth hormone treatment at a dose of 0.7 U/kg/week at 4 years of age with favorable results, increasing his height from the < 1st percentile to the 44th percentile.

Human Robinow syndrome (RS) and dominant omodysplasia type 2 (OMOD2), characterized by skeletal limb and craniofacial defects, are associated with heterozygous mutations in the Wnt receptor FZD2. However, as FZD2 can activate both canonical and non-canonical Wnt pathways, its precise functions and mechanisms of action in limb development are unclear. To address these questions, we generated mice harboring a single-nucleotide insertion in Fzd2 (Fzd2em1Smill), causing a frameshift mutation in the final Dishevelled-interacting domain. Fzd2em1Smill mutant mice had shortened limbs, resembling those of RS and OMOD2 patients, indicating that FZD2 mutations are causative. Fzd2em1Smill mutant embryos displayed decreased canonical Wnt signaling in developing limb mesenchyme and disruption of digit chondrocyte elongation and orientation, which is controlled by the β-catenin-independent WNT5A/planar cell polarity (PCP) pathway. In line with these observations, we found that disruption of FZD function in limb mesenchyme caused formation of shortened bone elements and defects in Wnt/β-catenin and WNT5A/PCP signaling. These findings indicate that FZD2 controls limb development by mediating both canonical and non-canonical Wnt pathways and reveal causality of pathogenic FZD2 mutations in RS and OMOD2 patients.

Frizzled 2 (FZD2) is a transmembrane Wnt receptor. We previously identified a pathogenic human FZD2 variant in individuals with FZD2-associated autosomal dominant Robinow syndrome. The variant encoded a protein with a premature stop and loss of 17 amino acids, including a region of the consensus dishevelled-binding sequence. To model this variant, we used zygote microinjection and i-GONAD-based CRISPR/Cas9-mediated genome editing to generate a mouse allelic series. Embryos mosaic for humanized Fzd2W553* knock-in exhibited cleft palate and shortened limbs, consistent with patient phenotypes. We also generated two germline mouse alleles with small deletions: Fzd2D3 and Fzd2D4. Homozygotes for each allele exhibit a highly penetrant cleft palate phenotype, shortened limbs compared with wild type and perinatal lethality. Fzd2D4 craniofacial tissues indicated decreased canonical Wnt signaling. In utero treatment with IIIC3a (a DKK inhibitor) normalized the limb lengths in Fzd2D4 homozygotes. The in vivo replication represents an approach for further investigating the mechanism of FZD2 phenotypes and demonstrates the utility of CRISPR knock-in mice as a tool for investigating the pathogenicity of human genetic variants. We also present evidence for a potential therapeutic intervention.

This study presents the routine prosection findings of a 73-year-old male cadaver, with the cause of death reported to be hypertension and respiratory failure. Deep thorax and abdomen dissection exposed profound external and internal anatomical abnormalities. Externally, the body exhibited the following: pectus excavatum; short-limbed dwarfism; and abnormalities of the head, face, and external genitalia. Most of these findings suggest that the donor had Robinow syndrome, a rare genetic disorder involving developmental delay and skeletal abnormalities akin to those found in this cadaver. The internal gross anatomical findings included the following: megacolon; hiatal hernia; bilateral inguinal hernias; laterally displaced right kidney with a fibrous adhesion extending from the inferior pole of the kidney to the inguinal canal; atypical branching of the abdominal aorta; superiorly displaced diaphragm; pulmonary hypoplasia; heart right of midline; and curved esophagus. Although determining the exact etiology of megacolon is difficult in a cadaveric specimen, it is important to investigate the physiological changes associated with it. Therefore, the aim of this study was to investigate the space-occupying pathology of megacolon and to discuss a potential connection between megacolon and Robinow syndrome.

Robinow syndrome is a rare congenital syndrome described in 1969 by Meinhard Robinow. The genetic background is heterogeneous - mutations of DVLI1, DVLI3, WNT5A genes (mild, autosomal dominant inheritance) or ROR2 gene (severe, autosomal recessive inheritance) are responsible for the syndrome. The syndrome is characterized by facial dysmorphism, skeletal defects, short stature, cardiovascular and urinary system abnormalities.
METHODS: We report nephrological and urological problems in two 4-year-old male patients with Robinow syndrome. The first patient has a horseshoe kidney located mainly on the right side, right vesicoureteral reflux grade II, dysfunctional voiding, buried penis, and retractile testicles. The second patient has recurrent urinary tract infections; diagnostic findings include left kidney duplication, grade II left vesicoureteral reflux, large posterior urethral diverticulum, dysfunctional voiding, buried penis, glanular hypospadias, and bilateral cryptorchidism.
CONCLUSIONS: Patients with Robinow syndrome require multidisciplinary care, including nephrology-urology care. Nephrological and urological manifestations in children with Robinow syndrome are diverse, and urinary tract defects may be atypical and complex.

OBJECTIVE: Robinow syndrome is a very rare syndrome characterized by short stature, extremity deformities, costovertebral abnormalities, renal/external genital malformations, and fetal facial appearance. It might be inherited by either autosomal dominant or severe recessive form. Diagnosis is generally established by the aid of genetic mutation and phenotypic findings. The urogenital component of the disease frequently presents with microgenitalia such as micropenis and/or cryptorchidism.
METHODS: Herein, a four-year-old boy with Robinow syndrome accompanied by incomplete bladder duplication is discussed.
RESULTS: The duplication in the bladder was screened by cystoscopy and corrective surgery was performed.
CONCLUSIONS: This rare manifestation is the first for urological findings of Robinow syndrome in literature.

The Dishevelled gene was first identified in Drosophila mutants with disoriented hair and bristle polarity and subsequent work has now demonstrated its importance in critical and diverse aspects of biology. Since those early discoveries, Dishevelled has been shown to coordinate a plethora of developmental and cellular processes that range from controlling cell polarity during gastrulation to partnering with chromatin modifying enzymes to regulate histone methylation at genomic loci. While the role of DVL in development is well-respected and the cytosolic function of DVL has been studied more extensively, its nuclear role continues to remain murky. In this review we highlight some of the seminal discoveries that have contributed to the field, but the primary focus is to discuss recent advances with respect to the nuclear role of Dishevelled. This nuclear function of Dishevelled is a dimension which is proving to be increasingly important yet remains enigmatic.