A MEN2A family with two asymptomatic carriers affected by unilateral renal agenesis

The genetic etiologies of bilateral renal agenesis

OBJECTIVE

The goal of this study was to review and analyze the medical literature for cases of prenatal and/or postnatally diagnosed bilateral renal agenesis (BRA) and create a comprehensive summary of the genetic etiologies known to be associated with this condition.

METHODS

A literature search was conducted as a scoping review employing Online Mendeliain Inheritance in Man, PubMed, and Cochrane to identify cases of BRA with known underlying genetic (chromosomal vs. single gene) etiologies and those described in syndromes without any known genetic etiology. The cases were further categorized as isolated versus non-isolated, describing additional findings reported prenatally, postnatally, and postmortem. Inheritance pattern was also documented when appropriate in addition to the reported timing of diagnosis and sex.

RESULTS

We identified six cytogenetic abnormalities and 21 genes responsible for 20 single gene disorders associated with BRA. Five genes have been reported to associate with BRA without other renal anomalies; sixteen others associate with both BRA as well as unilateral renal agenesis. Six clinically recognized syndromes/associations were identified with an unknown underlying genetic etiology. Genetic etiologies of BRA are often phenotypically expressed as other urogenital anomalies as well as complex multi-system syndromes.

CONCLUSION

Multiple genetic etiologies of BRA have been described, including cytogenetic abnormalities and monogenic syndromes. The current era of the utilization of exome and genome-wide sequencing is likely to significantly expand our understanding of the underlying genetic architecture of BRA.

Multiple endocrine neoplasia 2: an overview

This review article discusses the diagnosis and treatment of patients with multiple endocrine neoplasia type 2 (MEN2). The most common tumors associated with MEN2 are those of the parathyroid, thyroid, and adrenal glands. Additional manifestations include characteristic clinical phenotypes or features as described in the article. This review provides an overview of clinical manifestations, screening, diagnosis, treatment, and surveillance of patients with MEN2.

Total colonic aganglionosis and cleft palate in a newborn with Janus-cysteine 618 mutation of RET proto-oncogene: a case report

Background

Hirschsprung disease, the most important congenital colonic dysmotility in children results from neural crest migration, differentiation, proliferation, or apoptosis defects where the rearranged during transfection (RET)-Protooncogene pathway has a central role. Although palatal and retinal anomalies in the context of chromosomopathies and some mono−/oligogenic syndromes are reported associated with Hirschsprung disease the role of inactivating RET mutations in these cases is not clarified.

Case presentation

We report on a dysmorphic newborn with cleft palate and palatal synechia, who showed intestinal obstruction after 24 h of life. Transient ileostomy and surgical biopsies were performed to diagnose aganglionosis of the colon and last ileal loop. No chromosomal anomalies or copy number variations were found. We identified a paternal heterozygous germline mutation c.1852 T > C, which results in the substitution of cysteine by arginine in the RET-receptor tyrosine kinase (p.C618R mutation). There was no family history of Hirschsprung disease, but the father underwent surgery for medullary thyroid carcinoma and was affected by retinal dystrophy.

Conclusions

The occurrence of Hirschsprung disease and carcinoma shows how a single mutation may be responsible for adverse effects: gain and loss of function of the same receptor. Furthermore, it would be interesting to study its dual role in face and retina embryology, and to extend targeted investigations of RET hotspots in these developmental abnormalities to facilitate counselling, follow-up, and tumor prevention. Complex surgical procedures and genetic testing as well as socio-economic impact are a challenge for familiar compliance.

Unique association of multiple endocrine neoplasia 2A and congenital anomalies of the kidney and urinary tract in a child with a RET mutation

Pathogenic variants in the RET gene can cause isolated and multi-system diseases. We report a patient diagnosed prenatally with unilateral multicystic dysplastic kidney and genitourinary abnormality whose mother had multiple endocrine neoplasia type 2A (MEN2A). Targeted RET sequencing found the same pathogenic variant p.C618S in the child as her mother. The child is followed by paediatric nephrology for congenital anomalies of the kidney and urinary tract (CAKUT) and by endocrine oncology for surveillance for MEN2A-related endocrine tumours. While implicated in each of these conditions individually, RET variants have never been reported to cause MEN2A and CAKUT together. This child’s family history prompted RET sequencing, resulting in presymptomatic, personalised care for MEN2A. However, this case supports the idea that genetic screening of RET (and many other genes) in patients with CAKUT may lead to molecular diagnoses that potentially improve their health through precision care.

Development of the urogenital system is regulated via the 3'UTR of GDNF

Mechanisms controlling ureter lenght and the position of the kidney are poorly understood. Glial cell-line derived neurotrophic factor (GDNF) induced RET signaling is critical for ureteric bud outgrowth, but the function of endogenous GDNF in further renal differentiation and urogenital system development remains discursive. Here we analyzed mice where 3′ untranslated region (UTR) of GDNF is replaced with sequence less responsive to microRNA-mediated regulation, leading to increased GDNF expression specifically in cells naturally transcribing Gdnf. We demonstrate that increased Gdnf leads to short ureters in kidneys located in an abnormally caudal position thus resembling human pelvic kidneys. High GDNF levels expand collecting ductal progenitors at the expense of ureteric trunk elongation and result in expanded tip and short trunk phenotype due to changes in cell cycle length and progenitor motility. MEK-inhibition rescues these defects suggesting that MAPK-activity mediates GDNF’s effects on progenitors. Moreover, Gdnf   ^hyper mice are infertile likely due to effects of excess GDNF on distal ureter remodeling. Our findings suggest that dysregulation of GDNF levels, for example via alterations in 3′UTR, may account for a subset of congenital anomalies of the kidney and urinary tract (CAKUT) and/or congenital infertility cases in humans and pave way to future studies.

Targeted gene sequencing and whole-exome sequencing in autopsied fetuses with prenatally diagnosed kidney anomalies

Identification of fetal kidney anomalies invites questions about underlying causes and recurrence risk in future pregnancies. We therefore investigated the diagnostic yield of next-generation sequencing in fetuses with bilateral kidney anomalies and the correlation between disrupted genes and fetal phenotypes. Fetuses with bilateral kidney anomalies were screened using an in-house-designed kidney-gene panel. In families where candidate variants were not identified, whole-exome sequencing was performed. Genes uncovered by this analysis were added to our kidney panel. We identified likely deleterious variants in 11 of 56 (20%) families. The kidney-gene analysis revealed likely deleterious variants in known kidney developmental genes in 6 fetuses and TMEM67 variants in 2 unrelated fetuses. Kidney histology was similar in the latter 2 fetuses-presenting a distinct prenatal form of nephronophthisis. Exome sequencing identified ROBO1 variants in one family and a GREB1L variant in another family. GREB1L and ROBO1 were added to our kidney-gene panel and additional variants were identified. Next-generation sequencing substantially contributes to identifying causes of fetal kidney anomalies. Genetic causes may be supported by histological examination of the kidneys. This is the first time that SLIT-ROBO signaling is implicated in human bilateral kidney agenesis.

On the Origin of Cells and Derivation of Thyroid Cancer: C Cell Story Revisited

We will highlight and put into perspective new lineage tracing data from genetic studies in mice indicating that the genuine progenitors to C cells arise in the endoderm germ layer. This overturns the current concept of a neural crest origin of thyroid C cells referred to in every textbook and dedicated paper to this very day. As will become apparent, except for a single experiment, the neural crest theory has little or no support when the evolution and development of calcitonin-producing cells in the entire chordate family are considered. Instead, a unifying origin of all cells of the ultimobranchial bodies reopens questions on the histogenesis of certain thyroid pathologies previously difficult to explain. On this aspect, medullary thyroid cancer shows a stronger connection to gut neuroendocrine tumours than previously recognized. It is envisaged that novel factors implicated in C cell-derived tumour growth and progression will be discovered as the mechanisms that regulate lineage expansion of embryonic C cell precursors from pharyngeal endoderm are uncovered. We will not discuss why C cells go to the bother of burying themselves in the thyroid - this remains a mystery.

Clinical significance of RET mutation screening in a pedigree of multiple endocrine neoplasia type 2A

The clinical characteristics and RET proto-oncogene (RET‑PO) mutation status of a patient with multiple endocrine neoplasia type 2A pedigree (MEN2A) was analyzed with the aim of preliminarily exploring the molecular mechanisms and clinical significance of the disease. Clinical characteristics of a single MEN2A patient were analyzed. Genomic DNA was extracted from the peripheral blood of the proband and 10 family members. The 21 exons of RET‑PO were PCR amplified and the amplified products were sequenced. Of the family members, 5 exhibited a C634Y (TGC→TAC) missense mutation in exon 11 of RET‑PO, among which 2 family members were screened as mutation carriers, while the others did not exhibit clinical symptoms of the mutation. The screening and analysis of RET‑PO mutations for the MEN2A proband and the family members suggests potential clinical phenotypes and enables assessment of the risk of disease development, thus providing useful information for determining the surgical timing of preventive thyroid gland removal.

Bladder paraganglioma with renal agenesis: A possible new association and its implications in the light of REarranged in transfection gene genetics

Pheochromocytoma/paraganglioma and renal agenesis are commonly reported conditions. Their coexistence, however, is rare, with few cases reported. We report the case of a 21-year-old male who presented with painless hematuria. He was found to have congenital absent right kidney along with bladder mass on imaging. Examination including blood pressure was normal. He underwent cystoscopy that showed a solid looking tumor on the anterior wall. Paraganglioma was suspected due to intraoperative rise in blood pressure during resection and was confirmed on histopathology. Subsequently after work up and preoperative alpha blockade, patient underwent partial cystectomy and excision of the paravesical mass. Histopathology showed paraganglioma confined to bladder wall with surgical margins free and a paravesical mass that was seminal vesicle cyst. On follow-up, patient is normotensive and asymptomatic. This coexistence of paraganglioma and renal agenesis may have a common genetic mechanism in the form of REarranged in Transfection (RET) gene mutation. This is a well-characterized gene, mutations of which are known to be associated with both conditions. Current knowledge of the role of RET gene in both conditions is reviewed to put forth RET mutation as the possible common underlying genetic mechanism along with possible clinical implications of the combination.