Tryptophan-rich basic protein (WRB) mediates insertion of the tail-anchored protein otoferlin and is required for hair cell exocytosis and hearing.

The transmembrane recognition complex (TRC40) pathway mediates the insertion of tail-anchored (TA) proteins into membranes. Here, we demonstrate that otoferlin, a TA protein essential for hair cell exocytosis, is inserted into the endoplasmic reticulum (ER) via the TRC40 pathway. We mutated the TRC40 receptor tryptophan-rich basic protein (Wrb) in hair cells of zebrafish and mice and studied the impact of defective TA protein insertion. Wrb disruption reduced otoferlin levels in hair cells and impaired hearing, which could be restored in zebrafish by transgenic Wrb rescue and otoferlin overexpression. Wrb-deficient mouse inner hair cells (IHCs) displayed normal numbers of afferent synapses, Ca2+ channels, and membrane-proximal vesicles, but contained fewer ribbon-associated vesicles. Patch-clamp of IHCs revealed impaired synaptic vesicle replenishment. In vivo recordings from postsynaptic spiral ganglion neurons showed a use-dependent reduction in sound-evoked spiking, corroborating the notion of impaired IHC vesicle replenishment. A human mutation affecting the transmembrane domain of otoferlin impaired its ER targeting and caused an auditory synaptopathy. We conclude that the TRC40 pathway is critical for hearing and propose that otoferlin is an essential substrate of this pathway in hair cells.

The zebrafish pinball wizard gene encodes WRB, a tail-anchored-protein receptor essential for inner-ear hair cells and retinal photoreceptors.

KEY POINTS: The zebrafish pinball wizard (pwi) mutant is deaf and blind. The pwi phenotype includes a reduced auditory startle response and reduced visual evoked potentials, suggesting fatigue of synaptic release at ribbon synapses in hair cells and photoreceptors. The gene defective in the pwi mutant is WRB, a protein homologous to the yeast protein Get1, which is involved in the insertion of 'tail-anchored' membrane proteins. Many tail-anchored proteins are associated with synaptic vesicles, and both vesicles and synaptic ribbons are reduced in synaptic regions of hair cells in pwi. Abnormal processing of synaptic vesicle proteins important for ribbon synapses can explain the pwi phenotype. ABSTRACT: In a large-scale zebrafish insertional mutagenesis screen, we identified the pinball wizard (pwi) line, which displays a deafness and blindness phenotype. Although the gross morphology and structure of the pwi larval inner ear was near normal, acoustic startle stimuli evoked smaller postsynaptic responses in afferent neurons, which rapidly fatigued. In the retina, similarly, an abnormal electroretinogram suggested reduced transmission at the photoreceptor ribbon synapse. A functional deficit in these specialized synapses was further supported by a reduction of synaptic marker proteins Rab3 and cysteine-string protein (CSP/Dnajc5) in hair cells and photoreceptors, as well as by a reduction of the number of both ribbons and vesicles surrounding the ribbons in hair cells. The pwi gene encodes a homologue of the yeast Get1 and human tryptophan-rich basic (WRB) proteins, which are receptors for membrane insertion of tail-anchored (TA) proteins. We identified more than 100 TA proteins expressed in hair cells, including many synaptic proteins. The expression of synaptobrevin and syntaxin 3, TA proteins essential for vesicle fusion, was reduced in the synaptic layers of mutant retina, consistent with a role for the pwi/WRB protein in TA-protein processing. The WRB protein was located near the apical domain and the ribbons in hair cells, and in the inner segment and the axon of the photoreceptor, consistent with a role in vesicle biogenesis or trafficking. Taken together, our results suggest that WRB plays a critical role in synaptic functions in these two sensory cells, and that disrupted processing of synaptic vesicle TA proteins explains much of the mutant phenotype.

Ectopic pancreas in gallbladder. Clinical significance, diagnostic and therapeutic implications.

Ectopic or heterotopic pancreas is defined as the presence of pancreatic tissue in an anatomical place not related to the pancreas, being it most frequent locations the stomach and small bowel. Its finding in the gallbladder is exceptional. Since the first case was reported by Otschkin in 1916, about 30 cases have been described in literature. We report the case of a 43 years-old male patient who had an urgent laparoscopic cholecystectomy with the diagnosis of acute cholecystitis, which pathological study showed the existence of chronic cholecystitis with heterotopic pancreatic tissue in the gallbladder wall.

Prevalence of anti-T. canis antibodies in stray dogs in Mexico City.

UNLABELLED: Toxocara canis is a common intestinal helminth found in dogs. In humans, it is a cause of Visceral Larva Migrans (VLM), a zoonosis rarely studied in Mexico. The aim of this study is to examine, by means of the indirect haemaglutination test (IHAT), the prevalence of antibodies of T. canis in the serum of stray dogs in Mexico City. METHODS AND MATERIALS: 141 stray dog serum samples from three different districts of the city were analyzed: Iztacalco (49), Iztapalapa (49) and Coyoacan (43). In each location three study groups were formed. Group I with 35 dogs (less than a year old), Group II with 91 dogs (ages 1

Multiple nodal locoregional recurrence of pheochromocytoma.

INTRODUCTION: Malignancy is present in 10% of pheochromocytomas (PCC) and is defined as local/vascular infiltration of surrounding tissues or the presence of chromaffin cells deposits in distant organs. The presence of isolated nodal recurrence is very rare and only 7 cases have been reported in the medical literature. PRESENTATION OF THE CASE: The case of a 32-y male with a symptomatic recurrence of a previously operated (2-years ago) PCC is presented. Radiological and functional imaging studies confirmed the presence of multiple nodules in the surgical site. A radical left nephrectomy with extensive lymphatic clearance in order to get an R0 resection was performed. The pathologist confirmed the diagnosis of massive locoregional nodal invasion. DISCUSSION: A detailed histological report and a thorough genetic study must be considered in every operated PCC in order to identify mutations and profiles of risk for malignancy. When recurrence or metastastic disease is suspected, imaging and functional exams are done in order to obtain a proper staging. Radical surgery for the metastatic disease is the only treatment that may provide prolonged survival. If an R0 resection is not possible, then a debulking surgery is a good option when the benefit/risk ratio is acceptable. CONCLUSION: Isolated lymph nodal recurrence is very rare in malignant PCC, with only 7 cases previously published. The role of surgery is essential to get long-term survival because provides clinical and functional control of the disease.

The prevalence of Toxocara cati in domestic cats in Mexico City.

The faeces of 520 domestic cats, resident in the 16 municipal authorities of Mexico City, were analysed using the method of centrifuging with zinc sulphate (at 33%). Three hundred and ninety-nine animals lived in houses, 121 in apartments. For the purpose of this study they were divided into seven age groups, of 6 months each. Toxocara cati eggs were found in the faeces of 42.5% of the animals. 20.7% of apartment cats and 49.1% of house cats were infected. This difference in the rate of infection is statistically significant (P<0.002.) for the house cats. T. cati was found in all the age groups although most infection was found in animals less than 1 year old. The fact that infection occurred in the whole age range of the cats and in all the municipal authorities means that the risk of being contaminated with this helminth in Mexico City is high. As a consequence, the possibility of developing illness as a result of becoming a host to larva migrans is also high.

Contaminación parasitaria en heces de perros, recolectadas en calles de la ciudad de San Cristóbal de Las Casas, Chiapas, México / Parasitic contamination by dog feces collected from the streets of San Cristobal de Las Casas, Chiapas, Mexico

An analysis of canine faecal material collected in 13 different neighborhoods of the city of San Cristobal de Las Casas, Chiapas, Mexico, was carried out in order to know the frequency of contamination caused by Toxocara canis and other canine parasites. A total of 200 samples from streets, a traffic refuge and a park of the chosen neighborhoods in the city, were examined using the zinc sulphate method. Evidence of parasites was found in 37% (n = 74) of the samples. The frequency of I canis eggs was found to be 19 %, and that of Ancylostoma caninum eggs 18.5%; the oocistes of Isospora canis represented 2.5%. These results indicate that contamination of the soil of San Cristobal de Las Casas with these parasites, presents both a latent health risk for the population and visitors of this city, besides the poor image fecal contamination gives to national and foreign tourists.

Se realizó un estudio de materia fecal de perros en 13 barrios de la ciudad de San Cristóbal de Las Casas, Chiapas, México, para conocer la frecuencia de recontaminación causada por Toxocara canis y otros parásitos caninos. Se examinaron con el método de sulfato de zinc 200 muestras de materia fecal recolectadas en diferentes calles, un camellón y un parque de los barrios seleccionados en la ciudad. Se detectaron formas parasitarias en 37% (n = 74) de las muestras. La frecuencia de huevos de T. canis fue de 19.0% y la de Ancylostoma caninum, de 18.5%; la de ooquistes de Isospora canis de 2.5%. Los resultados indican que la contaminación de los suelos de la ciudad de San Cristóbal de Las Casas con parásitos de cánidos es un riesgo latente para la salud de los habitantes y visitantes de esta ciudad, además de la desagradable imagen que el fecalismo ofrece al turismo nacional y extranjero.

Inmunoepidemiología de la triquinelosis en niños de la Ciudad de México / The immunoepidemiology of trichinellosis in children in Mexico City

La triquinelosis constituye una enfermedad zoonótica cosmopolita de origen alimentario, la causa el nemátodo Trichinella spiralis. En México se ignora su frecuencia a pesar de los numerosos brotes epidémicos que se han presentado. El presente trabajo tiene como objetivo determinar, mediante hemaglutinación indirecta (HAI), la prevalencia de anticuerpos específicos contra antígenos de Trichinella spiralis, que se encontraron en el suero de una muestra de escolares que viven en la ciudad de México. Se analizaron 211 sueros de escolares de seis a doce años de edad, 111 (52.6 por ciento) varones y 110 (47.4 por ciento) niñas. Se formaron seis grupos de estudio, uno por cada grado escolar. El análisis inmunológico de los sueros se realizó con la microtécnica de hemaglutinación indirecta (HAI).Siete (3.3 por ciento) de los 211 sueros analizados resultaron positivos con títulos de dilución de 1:32; cinco sueros correspondieron a alumnos de 10 años de edad que cursaban el quinto grado escolar: cuatro varones y una niña; los otros dos sueros pertenecieron a niñas de nueve años de edad, del cuarto grado escolar. No se observó diferencia de reactividad respecto del sexo.La seropositividad obtenida en este estudio (3.3 por ciento) constituye un indicador de que la transmisión de triquinelosis está afectando a los habitantes de la población estudiada. Se analizan las posibles causas que favorecen esa transmisión.