Spinal neural tube formation and tail development in human embryos

Area of Science:

• Developmental Biology
• Human Embryology
• Spinal Cord Development

Background:

• Human primary and secondary neurulation, essential for spinal cord formation, remain poorly understood due to limited access to early embryos.
• Studying neurulation is critical for understanding congenital abnormalities and advancing regenerative medicine.

Purpose of the Study:

• To elucidate the processes of primary and secondary neurulation in human embryos.
• To establish normative data for human spinal cord development.
• To provide a basis for interpreting findings from human stem cell-derived organoids.

Main Methods:

• Analysis of 108 human embryos across Carnegie stages (CS) 10-18.
• Comparative analysis of neurulation processes with mouse and chick models.
• Investigation of gene expression (WNT3A, FGF8) and apoptosis in the embryonic tailbud.

Main Results:

• Primary neurulation completion and secondary neurulation mechanisms (single lumen formation) detailed in human embryos.
• Identified differences in the timing of somite formation and segmentation clock compared to mice.
• Observed secondary neural tube splitting in 60% of proximal human tail regions.
• Axial elongation termination linked to WNT3A/FGF8 downregulation and apoptosis in the tailbud.

Conclusions:

• Human spinal neurulation timing differs significantly from mouse and rat models.
• No evidence of a distinct 'transition zone' between primary and secondary neurulation in humans.
• Findings offer essential normative data for human organoid models of neurulation.