Loss of NFIA Impairs Adult Hippocampal Neurogenesis

Abstract

Adult hippocampal neurogenesis (AHN) is the process by which new neurons are continuously generated from neural stem and progenitor cells (NSPCs) in the adult dentate gyrus. AHN plays a pivotal role in cognitive functions, including learning, memory, and mood regulation. Transcription factors regulate AHN by maintaining the NSPC pool and facilitating lineage progression. The nuclear factor I (NFI) transcription factor family member NFIA is critical for neurogenesis and gliogenesis during early brain development, but its role in adult neurogenesis remains poorly understood. Here, we generated an inducible Nfia loss-of-function mouse model to investigate the role of NFIA in Ascl1-lineage adult-born neurons. By tracking lineage progression from NSPCs to mature neurons, we found that NFIA deletion significantly reduced neurogenesis. Populations of NSPCs, neuroblasts, and mature granule neurons were all similarly diminished, indicating a primary defect in NSPC maintenance. Behaviorally, NFIA loss impaired hippocampal-dependent contextual fear memory without affecting locomotor activity, anxiety levels, spatial memory, or cued fear memory. Our findings demonstrate that NFIA is crucial for AHN and hippocampus-dependent contextual memory, thereby providing insights into its role in adult neurogenesis.

Keywords: NFIA; adult hippocampal neurogenesis; dentate gyrus; hippocampus; learning and memory.

FIGURE 1

Loss of NFIA in Ascl1‐lineage cells impairs adult hippocampal neurogenesis. (A) Representative confocal images show tdTomato (tdT) reporter expression in the Ascl1‐CreERT2; Nfia ^flox/+ ; tdT (Control‐tdT) and the Ascl1‐CreERT2; Nfia ^flox/flox ; tdT (Nfia CKO‐tdT) mice 8 weeks post‐tamoxifen injection (16‐ to 17‐week‐old). CA1, cornu ammonis; DG, dentate gyrus. The boxes indicate areas of interest for panels (B–D). Scale bars: 250 μm. Quantification of tdT⁺ cells in the dentate gyrus is shown on the right: T(4) = 4.801, p = 0.0086. (B) Representative confocal images with co‐immunostaining for tdT, NFIA, and the neuroblast/immature neuron marker doublecortin (DCX). tdT⁺ DCX⁺ cells expressing NFIA are indicated by yellow arrowheads, while an NFIA‐negative cell is marked with a white arrow. Scale bars: 20 μm. Quantifications of NFIA deletion efficiency in tdT⁺ DCX⁺ cells are shown on the right: T(2) = 19.80, p = 0.0025. (C) Quantification of the total number of tdT⁺ DCX⁺ cells in the dentate gyrus: T(4) = 4.976, p = 0.0076. (D) Representative confocal images with co‐immunostaining for tdT and the neural stem and progenitor cell marker nestin (NES). tdT⁺ cells expressing NES are indicated by white arrowheads. Scale bars: 20 μm. Quantification of tdT⁺ NES⁺ neural stem and progenitor cells is shown on the right: T(4) = 4.102, p = 0.0148. (E) Representative confocal images with co‐immunostaining for tdT and the mature granule neuron marker calbindin (CALB1). tdT⁺ CALB1⁺ cells are indicated by white arrowheads. Scale bars: 20 μm. Quantification of tdT⁺ CALB1⁺ mature granule neurons is shown on the right: T(4) = 8.105, p = 0.0013. (F) A bar graph shows the relative composition of the three neuronal cell stages in control‐tdT and Nfia CKO‐tdT mice. Data are presented as scatter plots with all data points shown and error bars representing ±SD. Each data point (N) is an individual animal, whereby three sections were measured for each animal. Solid and open symbols represent data from female and male mice, respectively. Statistical analyses were performed using nested t‐test. *p < 0.05; **p < 0.01.

FIGURE 2

Loss of NFIA in Ascl1‐lineage cells impairs contextual fear memory. Mice (16‐ to 17‐week‐old) with the genotypes Nfia ^flox/flox (Flox), Ascl1‐CreERT2; Nfia ^flox/+ (CHet), and Ascl1‐CreERT2; Nfia ^flox/flox (CKO) 8 weeks post‐tamoxifen treatment were subject to (A) the open field assay, (B) the light–dark box assay, (C) the elevated zero maze test, (D) the spontaneous Y‐maze test, (E) the cued fear conditioning test, and (F) the context fear conditioning test. Data are presented as scatter plots with all data points shown and error bars representing ±SD. Each data point (N) is an individual animal. Solid and open symbols represent data from female and male mice, respectively. Statistical analyses were performed using unpaired t‐test with Welch's correction (A, B, and D) or ordinary one‐way ANOVA with Tukey post hoc test (C, E, and F). *p < 0.05; **p < 0.01. Statistics is reported as follows: (A) t(17.79) = 0.7818, p = 0.4446; (B) t(19.54) = 0.2521, p = 0.8036; (C) F(2, 43) = 0.8093, p = 0.4518; (D) t(20.30) = 0.6968, p = 0.4938; (E) pre‐tone: F(2, 53) = 1.030, p = 0.3641; tone: F(2, 53) = 1.504, p = 0.2316; (F) combined sex: F(2, 54) = 8.746, p = 0.0005; female: F(2, 24) = 5.807, p = 0.0088; male: F(2, 26) = 4.399, p = 0.0226.