Receptor tyrosine phosphatases guide vertebrate motor axons during development

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Receptor-type protein tyrosine phosphatases (RPTPs) are known to regulate axon growth in Drosophila.
• Vertebrate RPTPs, including type IIa (PTP-delta, PTP-sigma, LAR) and type III (PTPRO), are implicated in axon growth, but their developmental roles are unclear.
• PTPRO, PTP-delta, and PTP-sigma are expressed in chick motor neurons during axonogenesis.

Purpose of the Study:

• To investigate the in vivo roles of RPTPs in motor axon growth and guidance during vertebrate development.
• To determine the specific contributions of PTP-delta, PTP-sigma, and PTPRO to the development of limb nerves.

Main Methods:

• Utilized double-stranded RNA (dsRNA) interference to knock down RPTP expression in embryonic chick lumbar spinal cord.
• Employed in ovo electroporation for targeted delivery of dsRNA.
• Analyzed the effects on motor axon fasciculation, size, and presence of the anterior iliotibialis nerve.

Main Results:

• Knockdown of PTP-delta, PTP-sigma, or PTPRO individually led to abnormal fasciculation, reduced size, or absence of the anterior iliotibialis nerve.
• Interference with PTPRO resulted in the most severe developmental phenotypes.
• Combined knockdown of PTP-delta and PTPRO, or all three RPTPs, produced less severe phenotypes than PTPRO knockdown alone, suggesting a competitive interaction.

Conclusions:

• RPTPs, especially PTPRO, are essential for motor axon growth and guidance in the developing vertebrate limb.
• A competitive interaction between type IIa and type III RPTPs may regulate motor axon outgrowth, consistent with Drosophila findings.