cdon and boc affect trunk neural crest cell migration through a non-cell autonomous reduction of hedgehog signaling in zebrafish slow-twitch muscle

The immunoglobin superfamily members cdon and boc are transmembrane proteins implicated in regulating hedgehog signaling during vertebrate development. Recent work showing roles for these genes in axon guidance and neural crest cell migration further suggest that cdon/boc may play additional functions in regulating directed cell movements during development. Here we use novel and existing mutants to investigate a role for cdon and boc in zebrafish neural crest cell migration. We find that single cdon or boc mutant embryos exhibit normal neural crest phenotypes, but that neural crest migration is strikingly disrupted in double cdon/boc mutant embryos. We further show that this neural crest migration phenotype is associated with defects to the differentiation of slow-twitch muscle cells, and that this slow-twitch muscle phenotype is a consequence of reduced hedgehog signaling in mutant fish. While neural crest migratory ability is not affected in double mutant embryos, neural crest directionality is severely affected. These data suggest that neural crest migration defects are likely to be secondary to defects in slow-twitch muscle differentiation. Combined, our data add to a growing literature showing that cdon and boc act synergistically to promote hedgehog signaling during vertebrate development, and provide a foundation for using zebrafish to further study the function of these hedgehog receptor paralogs.

Pseudodiverticulum of the Cervical Esophagus With Remnant of Branchial Tissues in a Newborn: A Case Report

Congenital pseudodiverticula of the esophagus are very rare. This case report describes the presentation, management and histopathology of a peudodiverticulum of the cervical esophagus in a neonate. The infant presented with respiratory distress and a right neck mass that required surgical excision. Pathology revealed a pseudodiverticulum that contained ectopic thymic, thyroid, and parathyroid tissue within the wall of the lesion. The presence of ectopic tissues of branchial origin and an aberrant right subclavian artery suggest an error in branchial development and neural crest cell migration.

Inhibition of Cyclooxygenase-2 Alters Cranial Neural Crest Cell Migration in the Developing chick

A recent study from our lab revealed that inhibition of cyclooxygenase-2 exclusively reduces the level of PGE2 amongst the prostanoids and hamper the normal development of several structures, strikingly the cranial vault, in chick embryos. In order to unearth the mechanism behind the deviant development of cranial features, the expression pattern of various factors that are known to influence the cranial neural crest cell (CNCC) migration were checked in chick embryo after inhibiting the COX-2 activity using etoricoxib. The compromised level of cell adhesion molecules and their upstream regulators, namely CDH1, CDH2, MSX1, and TGF-β, observed in the etoricoxib treated embryos indicate that COX-2, through its downstream effector PGE2, regulates the expression of these factors perhaps to aid the migration of CNCC. The histological features and levels of FoxD3 as well as PCNA further consolidates the role of COX-2 in migration and survival of CNCC in developing embryo. The results of the current study indicate that the COX-2 plays a pivotal role in orchestrating the proliferation and migration of CNCC during embryonic development of chick.

ERBB4 exonic deletions on chromosome 2q34 in patients with intellectual disability or epilepsy

ERBB4 encodes the tyrosine kinase receptor HER4, a critical regulator of normal cell function and neurodevelopmental processes in the brain. One of the key ligands of HER4 is neureglin-1 (NRG1), and the HER4-NRG1 signalling pathway is essential in neural crest cell migration, and neuronal differentiation. Pharmacological inactivation of HER4 has been shown to hasten the progression of epileptogenesis in rodent models, and heterozygous ERBB4 null mice are shown to have cognitive deficits and delayed motor development. Thus far there is only a single case report in the literature of a heterozygous ERBB4 deletion in a patient with intellectual disability (ID). We identified nine subjects from five unrelated families with chromosome 2q34 deletions, resulting in heterozygous intragenic loss of multiple exons of ERBB4, associated with either non-syndromic ID or generalised epilepsy. In one family, the deletion segregated with ID in five affected relatives. Overall, this case series further supports that haploinsufficiency of ERBB4 leads to non-syndromic intellectual disability or epilepsy.

Oral manifestation of Waardenburg syndrome: a case report and review of the literature

Waardenburg syndrome is a rare autosomal dominant genetic disorder of neural crest cell migration. It is characterized by congenital sensorineural hearing loss, heterochromia iridis, depigmentation of hair and skin, and increased intercanthal distance. It is subdivided into four subtypes with I and II being most common. These subtypes are categorized based on genetic mutations. Although medical literature has well documented this syndrome, dental and radiographical findings have been rarely presented. In this case report and literature review, we have presented and discussed oral as well as head and neck radiology findings of a 20-year-old girl with Waardenburg syndrome.