Modeling development of genitourinary birth defects to understand disruption due to changes in gene dosage

Genitourinary development is a delicately orchestrated process that begins in the embryo. Once complete, the genitourinary system is a collection of functionally disparate organs spread throughout the abdominal and pelvic regions. These distinct organs are interconnected through an elaborate duct system which aggregates the organs' products to a common exit point. The complicated nature of the genitourinary system makes it highly susceptible to developmental disruptions that produce anomalies. In fact, genitourinary anomalies are among the most common class of human birth defects. Aside from congenital anomalies of the kidney and urinary tract (CAKUT), for males, these birth defects can also occur in the penis (hypospadias) and testis (cryptorchism), which impact male fertility and male mental health. As genetic technology has advanced, it has become clear that a subset of cases of genitourinary birth defects are due to gene variation causing dosage changes in critical regulatory genes. Here we first review the parallels between human and mouse genitourinary development. We then demonstrate how translational research leverages mouse models of human gene variation cases to advance mechanistic understanding of causation in genitourinary birth defects. We close with a view to the future highlighting upcoming technologies that will provide a deeper understanding of gene variation affecting regulation of genitourinary development, which should ultimately advance treatment options for patients.

Gene dosage changes in KCTD13 result in penile and testicular anomalies via diminished androgen receptor function

Despite the high prevalence of hypospadias and cryptorchidism, the genetic basis for these conditions is only beginning to be understood. Using array-comparative-genomic-hybridization (aCGH), potassium-channel-tetramerization-domain-containing-13 (KCTD13) encoded at 16p11.2 was identified as a candidate gene involved in hypospadias, cryptorchidism and other genitourinary (GU) tract anomalies. Copy number variants (CNVs) at 16p11.2 are among the most common syndromic genomic variants identified to date. Many patients with CNVs at this locus exhibit GU and/or neurodevelopmental phenotypes. KCTD13 encodes a substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3-ubiquitin-protein-ligase complex (BCR (BTB-CUL3-RBX1) E3-ubiquitin-protein-ligase complex (B-cell receptor (BCR) [BTB (the BTB domain is a conserved motif involved in protein-protein interactions) Cullin3 complex RING protein Rbx1] E3-ubiqutin-protein-ligase complex), which has essential roles in the regulation of cellular cytoskeleton, migration, proliferation, and neurodevelopment; yet its role in GU development is unknown. The prevalence of KCTD13 CNVs in patients with GU anomalies (2.58%) is significantly elevated when compared with patients without GU anomalies or in the general population (0.10%). KCTD13 is robustly expressed in the developing GU tract. Loss of KCTD13 in cell lines results in significantly decreased levels of nuclear androgen receptor (AR), suggesting that loss of KCTD13 affects AR sub-cellular localization. Kctd13 haploinsufficiency and homozygous deletion in mice cause a significant increase in the incidence of cryptorchidism and micropenis. KCTD13-deficient mice exhibit testicular and penile abnormalities together with significantly reduced levels of nuclear AR and SOX9. In conclusion, gene-dosage changes of murine Kctd13 diminish nuclear AR sub-cellular localization, as well as decrease SOX9 expression levels which likely contribute in part to the abnormal GU tract development in Kctd13 mouse models and in patients with CNVs in KCTD13.

Ventrally Fused Conjoined Twins (Omphaloischiopagus): A Roadmap to Successful Separation

Conjoined twining is one of the most fascinating and challenging situations which a pediatric surgeon may face in his career. Only few surgeons may have the opportunity to share in separation of such cases. In this report, we aim to share our experience with the successful separation of ventrally fused male conjoined twins (omphaloischiopagus). The case was thoroughly studied via preoperative cross-sectional imaging modalities (magnetic resonance imaging [MRI] and computed tomography [CT] angiography), complemented by data obtained from reviewing similar cases in the literature. A clear delineation of the complex anatomy was achieved preoperatively which proved to be well consistent with the operative findings. A detailed description of the operative procedure to divide/redistribute the shared abdominal/pelvic organs between both twins is provided. To the best of our knowledge, this is the first report to describe the detailed and unique internal anatomy of a common central phallus associating ischiopagus conjoined twins. The penis was centrally located in the perineum in between both twins with an open urethral plate. This common phallus had a peculiar configuration with four crura anchoring ischial bones of both twins together.