Compound heterozygous variants in MAPK8IP3 were detected in severe congenital hypotonia mimicking lethal spinal muscular atrophy

Mitogen-activated protein kinase 8-interacting protein 3 gene (MAPK8IP3) encodes the c-Jun-amino-terminal kinase-interacting protein 3 (JIP3) and is involved in retrograde axonal transport. Heterozygous de novo pathogenic variants in MAPK8IP3 result in a neurodevelopmental disorder with or without brain abnormalities and possible axonal peripheral neuropathy. Whole-exome sequencing was performed on an individual presenting with severe congenital muscle hypotonia of neuronal origin mimicking lethal spinal muscular atrophy. Compound heterozygous rare variants (a splice and a missense) were detected in MAPK8IP3, inherited from the healthy parents. Western blot analysis in a muscle biopsy sample showed a more than 60% decrease in JIP3 expression. Here, we suggest a novel autosomal recessive phenotype of a lower motor neuron disease caused by JIP3 deficiency.

Exosomes derived from M2 type tumor-associated macrophages promote osimertinib resistance in non-small cell lung cancer through MSTRG.292666.16-miR-6836-5p-MAPK8IP3 axis

Background

Osimertinib resistance limits the treatment of epidermal growth factor receptor-(EGFR)-mutated non-small-cell lung carcinoma (NSCLC). The mechanisms of osimertinib resistance need to be elucidated to determine alternative treatment strategies. This study explores the role of M2 type tumor-associated macrophage (TAM)-derived exosomal MSTRG.292666.16 in osimertinib resistance, and its related competing endogenous RNA (ceRNA) mechanism.

Methods

M2 type TAMs were induced with 200 ng/mL phorbol 12-myristate 13-acetate, 20 ng/mL IL-4 and IL-13, and M2 type macrophage markers were measured by RT-qPCR. Next, the exosomes were isolated and characterized. Tumor formation in nude mice was conducted using H1975 cells under different treatment conditions. Small RNA sequencing was performed on exosomes derived from sensitive and resistant plasma, and ceRNA networks were constructed. Fluorescence in situ hybridization was used to observe the localization of MSTRG.292666.16, and a ceRNA network (MSTRG.292666.16-miR-6836-5p-MAPK8IP3) was selected for further validation.

Results

M2 type TAMs, and M2 type TAM-derived exosomes were successfully induced and isolated. Nude mice results showed that M2 type TAM-derived exosomes and MSTRG.292666.16 overexpression significantly increased tumor volume after administration of osimertinib for 4 weeks. M2 type TAMs were found in the resistant plasma, and MSTRG.292666.16 localized in the cytoplasm of H1975 cells. In addition, the genes in the ceRNA networks were significantly enriched in eight GO terms and seven KEGG pathways, including the MAPK signaling pathway. Subsequently, the levels of MSTRG.292666.16 and MAPK8IP3 significantly increased in both resistant plasma-derived exosomes and M2 type TAM-derived exosomes, while miR-6836-5p levels were significantly reduced. Finally, MSTRG.292666.16, miR-6836-5p, and MAPK8IP3 were part of the same network.

Conclusions

M2 type TAM-derived exosomes promoted osimertinib resistance in NSCLC by regulating the MSTRG.292666.16/miR-6386-5p/MAPK8IP3 axis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02509-x.

Syd/JIP3 controls tissue size by regulating Diap1 protein turnover downstream of Yorkie/YAP

How organisms control organ size is not fully understood. We found that Syd/JIP3 is required for proper wing size in Drosophila. JIP3 mutations are associated with organ size defects in mammals. The underlying mechanisms are not well understood. We discovered that Syd/JIP3 inhibition results in a downregulation of the inhibitor of apoptosis protein 1 (Diap1) in the Drosophila wing. Correspondingly, Syd/JIP3 deficient tissues exhibit ectopic cell death and yield smaller wings. Syd/JIP3 inhibition generated similar effects in mammalian cells, indicating a conserved mechanism. We found that Yorkie/YAP stimulates Syd/JIP3 in Drosophila and mammalian cells. Notably, Syd/JIP3 is required for the full effect of Yorkie-mediated tissue growth. Thus Syd/JIP3 regulation of Diap1 functions downstream of Yorkie/YAP to control growth. This study provides mechanistic insights into the recent and perplexing link between JIP3 mutations and organ size defects in mammals, including in humans where de novo JIP3 variants are associated with microcephaly.

De Novo Variants in MAPK8IP3 Cause Intellectual Disability with Variable Brain Anomalies

Using exome sequencing, we have identified de novo variants in MAPK8IP3 in 13 unrelated individuals presenting with an overlapping phenotype of mild to severe intellectual disability. The de novo variants comprise six missense variants, three of which are recurrent, and three truncating variants. Brain anomalies such as perisylvian polymicrogyria, cerebral or cerebellar atrophy, and hypoplasia of the corpus callosum were consistent among individuals harboring recurrent de novo missense variants. MAPK8IP3 has been shown to be involved in the retrograde axonal-transport machinery, but many of its specific functions are yet to be elucidated. Using the CRISPR-Cas9 system to target six conserved amino acid positions in Caenorhabditis elegans, we found that two of the six investigated human alterations led to a significantly elevated density of axonal lysosomes, and five variants were associated with adverse locomotion. Reverse-engineering normalized the observed adverse effects back to wild-type levels. Combining genetic, phenotypic, and functional findings, as well as the significant enrichment of de novo variants in MAPK8IP3 within our total cohort of 27,232 individuals who underwent exome sequencing, we implicate de novo variants in MAPK8IP3 as a cause of a neurodevelopmental disorder with intellectual disability and variable brain anomalies.