The schizophrenia-associated missense variant rs13107325 regulates dendritic spine density

Abstract

The missense variant rs13107325 (C/T, p.Ala391Thr) in SLC39A8 consistently showed robust association with schizophrenia in recent genome-wide association studies (GWASs), suggesting the potential pathogenicity of this non-synonymous risk variant. Nevertheless, how this missense variant confers schizophrenia risk remains unknown. Here we constructed a knock-in mouse model (by introducing a threonine at the 393th amino acid of mouse SLC39A8 (SLC39A8-p.393T), which corresponds to rs13107325 (p.Ala391Thr) of human SLC39A8) to explore the potential roles and biological effects of this missense variant in schizophrenia pathogenesis. We assessed multiple phenotypes and traits (associated with rs13107325) of the knock-in mice, including body and brain weight, concentrations of metal ions (including cadmium, zinc, manganese, and iron) transported by SLC39A8, blood lipids, proliferation and migration of neural stem cells (NSCs), cortical development, behaviors and cognition, transcriptome, dendritic spine density, and synaptic transmission. Many of the tested phenotypes did not show differences in SLC39A8-p.393T knock-in and wild-type mice. However, we found that zinc concentration in brain and blood of SLC39A8-p.393T knock-in mice was dysregulated compared with wild-types, validating the functionality of rs13107325. Further analysis indicated that cortical dendritic spine density of the SLC39A8-p.393T knock-in mice was significantly decreased compared with wild-types, indicating the important role of SLC39A8-p.393T in dendritic spine morphogenesis. These results indicated that SLC39A8-p.393T knock-in resulted in decreased dendritic spine density, thus mimicking the dendritic spine pathology observed in schizophrenia. Our study indicates that rs13107325 might confer schizophrenia risk by regulating zinc concentration and dendritic spine density, a featured characteristic that was frequently reported to be decreased in schizophrenia.

Cross-ancestry genome-wide association study and systems-level integrative analyses implicate new risk genes and therapeutic targets for depression

“…Open field test is a method to evaluate movement and anxious behaviors of animals in novel environments. Open field test was conducted as previously described 93 . Briefly, the open field arena (Length: 40 cm; Width: 40 cm; Height: 40 cm) was divided into sixteen squares using SuperMaze software, the four squares at corner were defined as corner areas, and the four squares at center were defined as central areas.…”

“…The light-dark transition test uses the conflict between innate aversion to light areas and exploratory behavior of rodents to study anxious behaviors of mice. Light-dark transition test was conducted as previously described 93 . Briefly, the apparatus consists of two same boxes (length: 20 cm; width: 15 cm; height: 25 cm), a light and dark box.…”

“…Elevated plus maze investigates the anxiety state of animals based on the contradictory behaviors of exploring the new environment and the fear of hanging in open arms. Elevated plus maze was conducted as previously described 93 . Briefly, the elevated plus maze apparatus is above the ground 75 cm and consists of four arms (two close arms (length: 35 cm; width: 5 cm; height: 15 cm) and two open arms (length: 35 cm; width: 5 cm) and a cross area (length: 5; width: 5 cm).…”

“…Y-maze investigates spatial working memory in mice based on spontaneous tendency to explore new environments. Y maze test was conducted as previously described 93 . Briefly, Y-shaped geometric arena with three arms (arm length, width, height: 35 cm, 5 cm, 15 cm) were defined as A, B, and C arms, and the angle between arm is 120°.…”

“…Tail suspension test was used to detect desire to survive of mouse in a desperate situation, the mouse frequently has no desire to survive in depressive state. Tail suspension test was conducted as previously described 93 . Briefly, mouse tail (about 1 cm) was fixed on the suspension hook in chamber box (length: 20 cm; width: 20 cm; heigh: 32 cm) using adhesive tape, and let the mouse body freely hung down in the air at a fixed height for 6 mins.…”