Developmental expression patterns of neuronal growth genes 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 using central nervous system transcriptomic data from the Bgee v15 database. After excluding samples with imprecise age, unassignable whole-brain samples, and cross-accession duplicates, 433 samples were categorized into six developmental stages: late embryonic, neonate, juvenile, prime adult, late adult, and senior, and examined across forebrain and hindbrain divisions. Spearman correlation assessed relationships between expression and stage, and one-way ANOVA on log2(TPM+1) values with Tukey's post-hoc tests and Benjamini-Hochberg correction assessed differences across stages. Expression trajectories differed by gene and region. GAP43 showed the strongest age-related association, a moderate negative correlation with higher expression in earlier stages. MAP1B showed a similar but weaker downward trend. SEMA3B demonstrated a moderate positive correlation with stage, while GAL showed a weak but statistically significant decline. Forebrain regions exhibited greater developmental variability than hindbrain regions, with GAP43 and MAP1B peaking earlier in life and GAL and SEMA3B showing more modest, regionally specific variation. Neuronal growth-related genes do not follow a uniform developmental trajectory; expression patterns are gene-specific and region-dependent, highlighting temporally and anatomically distinct transcriptional programs in the healthy human brain. These findings are descriptive, and hindbrain and sex-stratified comparisons, based on small, imbalanced subgroups, are exploratory.