AP-4 loss in CRISPR-edited zebrafish affects early embryo development

Area of Science:

• Cell Biology
• Developmental Biology
• Genetics

Background:

• Mutations in adaptor protein 4 (AP-4) are linked to severe neurological disorders, including spastic paraplegia, microcephaly, and intellectual disabilities.
• AP-4's role in membrane trafficking, particularly its cargo ATG9A (an autophagy protein), is crucial, but organismal-level understanding is limited due to gene loss in common model systems.
• Zebrafish (Danio rerio) possess conserved AP-4 genes, making them a suitable model for studying AP-4's developmental and neurological functions.

Purpose of the Study:

• To investigate the effects of AP-4 and tepsin gene loss on zebrafish embryo development using CRISPR-ExoCas9 gene editing.
• To explore the impact of AP-4 single gene knockouts on the expression of autophagy-related genes (atg9a and map1lc3b) in zebrafish embryos.
• To establish zebrafish as a model organism for dissecting AP-4's function in membrane trafficking and autophagy.

Main Methods:

• CRISPR-ExoCas9 gene editing was employed to create single gene knockouts for AP-4 and tepsin in zebrafish embryos.
• Zebrafish embryos were analyzed at 24 hours post-fertilization (hpf) for developmental abnormalities.
• Quantitative analysis of atg9a and map1lc3b gene expression was performed in gene-edited zebrafish embryos.

Main Results:

• Single gene editing of AP-4 or tepsin resulted in observable abnormal head morphology and neural necrosis in zebrafish embryos at 24 hpf.
• The study provides the first evidence of altered expression patterns for autophagy genes atg9a and map1lc3b following AP-4 gene knockout in zebrafish embryos.
• These findings highlight the critical role of AP-4 in early embryonic development and neurogenesis.

Conclusions:

• Zebrafish gene editing effectively models the developmental consequences of AP-4 dysfunction, mirroring aspects of human neurological disorders.
• AP-4 plays a significant role in regulating autophagy gene expression during early development.
• Zebrafish represent a valuable and adaptable model system for future research into AP-4-mediated membrane trafficking and autophagy in the context of complex diseases.