Neuropathologic research strategies in holoprosencephaly

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Holoprosencephaly (HPE) is a congenital disorder characterized by incomplete forebrain division.
• Traditional classification relies on morphology (alobar, semilobar, lobar), but genetic factors are increasingly recognized.
• Existing genetic findings highlight a ventrodorsal expression gradient for key HPE genes.

Purpose of the Study:

• To propose hypotheses for the pathogenesis of HPE clinical features based on gene expression gradients.
• To suggest neuropathologic approaches for testing these hypotheses.
• To advocate for a new HPE classification integrating morphologic and genetic data.

Main Methods:

• Review and synthesis of existing literature on HPE genetics and neuropathology.
• Hypothetical modeling of gene expression gradients (ventrodorsal, rostrocaudal, mediolateral) in neural development.
• Correlation of proposed gradient effects with observed HPE phenotypes.

Main Results:

• Gene expression gradients along rostrocaudal and mediolateral axes, in addition to ventrodorsal, are hypothesized to be crucial.
• Rostocaudal gradients may explain midfacial hypoplasia and specific forebrain structural abnormalities.
• Mediolateral gradients may account for variations in cerebral cortical organization and associated cognitive/epileptic outcomes.

Conclusions:

• A comprehensive understanding of HPE pathogenesis requires considering multi-axial gene expression gradients.
• These gradients offer explanations for diverse clinical presentations, including neurodevelopmental and neuroendocrine issues.
• A revised classification system for holoprosencephaly integrating genetic and morphologic data is necessary.