The subcommissural organ regulates brain development via secreted peptides

I. Research Background and Purpose The subcommissural organ (SCO) is a glandular structure located at the entrance of the ventricular system, which is present in humans and other vertebrates, but its function has not been fully elucidated. Previous studies have suggested that the SCO may be involved in the regulation of neural development and the maintenance of the internal environment of the cerebrospinal fluid, but most of these studies have relied on in vitro cell culture or organ transplantation models, with relatively few studies on its function at the level of live animals. This study aimed to specifically eliminate SCO cells in mice through genetic manipulation to explore the key role of the SCO in brain development.

II. Research Objects and Methods 1. Through transcriptomic analysis, three genes (sspo, car3, and spdef) that are highly specifically expressed in the SCO were selected. 2. Using the promoters of these three genes to drive the expression of Cre recombinase, four mouse strains (spdef-cre, car3-cre, sspo-cre, and sspo-creer) were constructed to specifically label or eliminate SCO cells. 3. By crossing these Cre strains with strains carrying the Cre-dependent diphtheria toxin gene (dta), SCO cells were specifically eliminated, and the phenotypic changes after SCO deficiency were studied. 4. RNA-seq and proteomics were used to identify several neuropeptides secreted by the SCO, and their effects on neuronal development were investigated. 5. These neuropeptides were administered to SCO-deficient mice to observe their rescuing effects on developmental defects.

III. Main Research Findings 1. In the sspo-cre;dta mice with SCO deficiency, severe cerebellar developmental abnormalities were observed, such as hydrocephalus, defects in neuronal positioning, and abnormal extension of neurite fibers. 2. SCO deficiency led to decreased neuronal survival rates, impaired dendritic branching development, and other abnormalities, indicating that the SCO plays a crucial role in regulating neural development. 3. Through proteomic analysis, three neuropeptides (thymosin beta 4, thymosin beta 10, and NP24) were identified as being enriched and secreted by the SCO. 4. These three peptides promote neuronal development, and exogenous supplementation partially rescued the developmental defects in SCO-deficient mice, suggesting that they are important effector molecules through which the SCO regulates neural development.

IV. Research Significance 1. This study is the first to elucidate the important regulatory role of the SCO in brain development at the level of live animals, laying the foundation for understanding its functions in normal physiology and disease. 2. A new mechanism by which the SCO mediates downstream developmental effects through the secretion of specific neuropeptides has been identified. 3. This research provides new molecular targets for exploring the pathological processes of developmental defects such as congenital hydrocephalus caused by SCO abnormalities.

This study systematically reveals the novel function of the cerebellar subcommissural organ in regulating neural development and its underlying mechanisms. It has significant value for fully understanding the physiological significance of this evolutionarily conserved and important brain region.