[Effects of Thap6 gene knockout on emotional and social behaviors in mice]

THAP domain-containing protein 6 (THAP6) is a member of the THAP family and contains a conserved THAP zinc-finger domain, allowing it to regulate gene expression as a transcription factor. Previous studies have shown that THAP6 may be involved in macrophage activation and transcriptional regulation related to social stimuli; however, whether THAP6 affects emotional behavior and brain tissue structure has not yet been reported. This study aims to clarify the effects of Thap6 gene deletion on emotional behaviors in mice, preliminarily explore the effects of Thap6 gene knockout on mouse brain tissue, and provide experimental evidence for revealing the potential role of THAP6 in neuropsychiatric disorders.

A whole-body Thap6 knockout mouse model was generated using CRISPR/Cas9 technology. Genotyping was performed to select heterozygous Thap6 knockout (Thap6^+/-; n=8) and wild-type (WT; n=10) male C57BL/6J mice as study subjects. After the mice reached adulthood, motor and balance abilities were assessed using the rotarod test; general locomotor activity and exploratory ability were evaluated using the open-field test; depression-like behaviors were assessed using the sucrose preference test and tail suspension test; anxiety-like behavior was evaluated using the elevated plus-maze test; and social behavior was assessed using the three-chamber social test. After behavioral assessments, mouse brain tissues were collected, and hematoxylin and eosin (HE) staining and Nissl staining were used to observe changes in brain microstructure and neuronal number.

Behavioral results showed that, compared with WT mice, Thap6^+/- mice had a significantly lower percentage of entries into the open arms in the elevated plus maze test (t=2.516, P=0.024) and a significantly higher average movement speed in the open arms (t=3.045, P=0.013). In the three-chamber social test, the sociability index (t=4.350, P<0.001) and social preference index (t=2.732, P=0.014) of Thap6^+/- mice were significantly lower than those of WT mice. No statistically significant differences were observed between the 2 groups in other behavioral indicators (all P>0.05). HE staining of brain tissues showed scattered abnormal cell morphology, loose cytoplasm, and blurred nuclei in the cortex of Thap6⁺/⁻ mice; loosely arranged neurons, enlarged intercellular spaces, and extensive vacuole formation in the amygdala; disordered arrangement of cerebellar Purkinje cells, unclear boundaries, swelling and dissolution of some nuclei, and cell loss; and loss of neuronal nucleoli and partial cellular pyknosis in the substantia nigra. In the hippocampus of Thap6⁺/⁻ mice, neurons were orderly arranged, with relatively good cell morphology, a larger number of cells, and compact arrangement. Nissl staining showed that the number of neurons in the hippocampal dentate gyrus region was significantly increased in Thap6⁺/⁻ mice (U=0, P=0.029), whereas morphological abnormalities and reduced neuronal numbers were observed in the cortex, amygdala, cerebellum, and substantia nigra (all U=0, P=0.029).

Thap6 gene knockout leads to anxiety-like behavior and social behavioral deficits in mice. It also causes structural abnormalities and reductions in neuronal number across multiple brain regions. This study systematically reveals, for the first time, the important role of THAP6 in the regulation of emotional and social behaviors, provides new evidence for understanding the functional differentiation of THAP family proteins in the central nervous system, and suggests that Thap6 knockout mice may serve as a novel animal model for studying neuropsychiatric disorders related to anxiety and social deficits.