Aberrant ERK signaling in astrocytes impairs learning and memory in RASopathy-associated BRAF mutant mouse models
Minkyung Kang, … , Chul Hoon Kim, Yong-Seok Lee
Minkyung Kang, … , Chul Hoon Kim, Yong-Seok Lee
Published February 18, 2025
Citation Information: J Clin Invest. 2025;135(8):e176631. https://doi.org/10.1172/JCI176631.
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Research Article Development Neuroscience

Aberrant ERK signaling in astrocytes impairs learning and memory in RASopathy-associated BRAF mutant mouse models

Abstract

RAS/MAPK pathway mutations often induce RASopathies with overlapping features, such as craniofacial dysmorphology, cardiovascular defects, dermatologic abnormalities, and intellectual disabilities. Although B-Raf proto-oncogene (BRAF) mutations are associated with cardio-facio-cutaneous (CFC) syndrome and Noonan syndrome, it remains unclear how these mutations impair cognition. Here, we investigated the underlying neural mechanisms using several mouse models harboring a gain-of-function BRAF mutation (K499E) discovered in RASopathy patients. We found expressing BRAF K499E (KE) in neural stem cells under the control of a Nestin-Cre promoter (Nestin;BRAFKE/+) induced hippocampal memory deficits, but expressing it in excitatory or inhibitory neurons did not. BRAF KE expression in neural stem cells led to aberrant reactive astrogliosis, increased astrocytic Ca2+ fluctuations, and reduced hippocampal long-term depression (LTD) in mice. Consistently, 3D human cortical spheroids expressing BRAF KE also showed reactive astrogliosis. Astrocyte-specific adeno-associated virus–BRAF KE (AAV-BRAF KE) delivery induced memory deficits and reactive astrogliosis and increased astrocytic Ca2+ fluctuations. Notably, reducing extracellular signal-regulated kinase (ERK) activity in astrocytes rescued the memory deficits and altered astrocytic Ca2+ activity of Nestin;BRAFKE/+ mice. Furthermore, reducing astrocyte Ca2+ activity rescued the spatial memory impairments of BRAF KE–expressing mice. Our results demonstrate that ERK hyperactivity contributes to astrocyte dysfunction associated with Ca2+ dysregulation, leading to the memory deficits of BRAF-associated RASopathies.

Authors

Minkyung Kang, Jihye Choi, Jeongho Han, Toshiyuki Araki, Soo-Whee Kim, Hyun-Hee Ryu, Min-Gyun Kim, Seoyeon Kim, Hanbyul Jang, Sun Yong Kim, Kyoung-Doo Hwang, Soobin Kim, Myeongjong Yoo, Jaegeon Lee, Kitae Kim, Pojeong Park, Ja Eun Choi, Dae Hee Han, Yujin Kim, Jeongyeon Kim, Sunghoe Chang, Bong-Kiun Kaang, Jung Min Ko, Keun-Ah Cheon, Joon-Yong An, Sang Jeong Kim, Hyungju Park, Benjamin G. Neel, Chul Hoon Kim, Yong-Seok Lee

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Figure 4

Astrocyte-specific BRAF KE induces reactive astrogliosis and hippocampal memory deficits.

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Astrocyte-specific BRAF KE induces reactive astrogliosis and hippocampal...
(A) Schematic illustrating the experimental approach. AAV5-GFAP-GFP (GFP) or AAV5–GFAP–HA–BRAF KE (BRAF KE) was injected into the hippocampal CA1 region of adult C57BL/6 mice. (B) Latency for mice injected with GFP or BRAF KE to find the hidden-platform during MWM training trials. (C) Representative trajectories of GFP- or BRAF KE–injected mice during the MWM probe trial. (D) Quadrant occupancy, (E) proximity to the platform, or (F) number of target zone entries of the mice in C. (G) Representative immunohistochemical images from GFP- or BRAF KE–injected mice. Slices were immunostained for HA (green), GFAP (magenta), and p-ERK1/2 (red). Arrows indicate double labeling of GFAP and p-ERK1/2. Scale bars: 50 μm. (H) GFAP-expressing cells from the mice in G. (I) Representative Sholl analyses of an astrocyte in the stratum radiatum of the GFAP-stained image in G. (J) The number of process intersections and (K) the sum of process intersections for GFAP-positive astrocytes in the stratum radiatum of GFP- or BRAF KE–injected mice. (L) Representative immunoblot image of hippocampal lysates from mice injected with GFP or BRAF KE. (M) p-ERK1/2 expression normalized to ERK1/2 expression in hippocampal lysates or (N) GFAP expression normalized to GAPDH expression from the mice in L. Data are expressed as means ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.