cdh23 affects congenital hearing loss through regulating purine metabolism

Introduction

The pathogenic gene CDH23 plays a pivotal role in tip links, which is indispensable for mechanoelectrical transduction in the hair cells. However, the underlying molecular mechanism and signal regulatory networks that influence deafness is still largely unknown.

Methods

In this study, a congenital deafness family, whole exome sequencing revealed a new mutation in the pathogenic gene CDH23, subsequently; the mutation has been validated using Sanger sequencing method. Then CRISPR/Cas9 technology was employed to knockout zebrafish cdh23 gene. Startle response experiment was used to compare with wide-type, the response to sound stimulation between wide-type and cdh23-/-. To further illustrate the molecular mechanisms underlying congenital deafness, comparative transcriptomic profiling and multiple bioinformatics analyses were performed.

Results

The YO-PRO-1 assay result showed that in cdh23 deficient embryos, the YO-PRO-1 signal in inner ear and lateral line neuromast hair cells were completely lost. Startle response experiment showed that compared with wide-type, the response to sound stimulation decreased significantly in cdh23 mutant larvae. Comparative transcriptomic showed that the candidate genes such as atp1b2b and myof could affect hearing by regulating ATP production and purine metabolism in a synergetic way with cdh23. RT-qPCR results further confirmed the transcriptomics results. Further compensatory experiment showed that ATP treated cdh23-/- embryos can partially recover the mutant phenotype.

Conclusion

In conclusion, our study may shed light on deciphering the principal mechanism and provide a potential therapeutic method for congenital hearing loss under the condition of CDH23 mutation.

Acute cerebral hemorrhage changes the nocturnal surge of plasma melatonin in humans

The diurnal rhythm of plasma melatonin was studied in 46 Chinese patients with acute cerebral hemorrhage. The state of consciousness of each patient was assessed clinically. The individual sites of lesion were determined by computerized tomography scanning. One to five days after stroke, blood samples were collected by venipuncture at 1000 and 1400 h in the daytime and 0200 and 0400 h at night. Plasma melatonin was extracted by dichloromethane and determined by radioimmunoassay. It was found that patients with lesions in the brain stem or in the third and lateral ventricles had melatonin levels significantly different from the other subjects in that these values were lower and lacking a nocturnal rise. These results are consistent with the presumptive retina-pineal pathway proposed in humans. Dramatic blunting or obliteration of the nocturnal melatonin surge in the blood was also observed in some patients with lesions in the frontal lobe, fronto-parietal lobe, parieto-temporal lobe, and basal ganglia. These brain regions are not involved in the retina-pineal pathway described in rodents or humans. Thus, our results suggest that brain regions other than the presumptive retina-pineal neural pathway may play an important role in the generation and/or regulation of the diurnal production and/or secretion of pineal melatonin in humans. However, a global functional disturbance caused by cerebral hemorrhage cannot be ruled out in some cases. It should be noted that many of the lesions leading to a change in the nocturnal rise of plasma melatonin were unilateral lesions. The significance of this finding is presently unknown. In addition, patients without a nocturnal rise of plasma melatonin were mostly comatose. They had lesions in the basal ganglion, fronto-parietal lobe, brain stem, and lateral and third ventricles. The latter findings suggest that in the brain, certain regions responsible for the state of consciousness of the individual may also be important to the dirunal rhythm of pineal melatonin secretion.