DEVELOPMENTAL EXPRESSION PATTERNS OF NEURONAL GROWTH GENES (GAL, GAP43, SEMA3B, MAP1B) ACROSS HUMAN BRAIN STAGES USING BGEE TRANSCRIPTOMIC DATA

Human brain maturation from prenatal life through aging is driven by tightly regulated gene expression programs supporting neuronal differentiation, axonal growth, and synaptic development. Although individual neuronal growth–related genes have been studied, limited work describes how they vary across defined human life stages and major brain regions. This study evaluated developmental expression trajectories of GAP43, MAP1B, SEMA3B, and GAL in healthy human brain tissue. Human central nervous system transcriptomic data were obtained from the Bgee v15 database. After exclusion of samples lacking precise age assignment, 481 samples were categorized into six developmental stages: late embryonic, neonate, juvenile, prime adult, late adult, and senior. Expression was examined across forebrain and hindbrain divisions. Correlation analyses evaluated relationships between expression and developmental stage, and one-way ANOVA assessed expression differences across stages. Expression trajectories differed by gene and region. GAP43 demonstrated the strongest age-related association, showing a moderate negative correlation with higher expression in earlier developmental stages. MAP1B showed a similar but slightly weaker downward trend. SEMA3B demonstrated a weak positive correlation with developmental stage, while GAL expression showed only modest directional change. Forebrain regions exhibited greater developmental variability than hindbrain regions. GAP43 and MAP1B expression peaked earlier in life, whereas GAL and SEMA3B demonstrated more modest, regionally specific variation. Neuronal growth–related genes do not follow a uniform developmental trajectory across the human lifespan. Instead, expression patterns are gene-specific and region-dependent, highlighting temporally and anatomically distinct transcriptional programs in the healthy human brain.