The cleft palate-associated gene Midline1 plays a role in mouse palatal development by regulating MMP8 and Snail proteins

Abstract

Objective

This study aimed to investigate the role of the Midline1 gene in secondary palate development by analyzing its expression and function in palatal shelf fusion and morphology.

Design

Initially, twenty mouse embryos were collected for each of the embryonic stages E13.5, E13.75, and E14.5. Whole-mount in situ hybridization was performed approximately ten times to optimize the experimental protocol and to analyze the expression pattern of Midline1 (MID1) in the palatal tissues at these developmental stages. Subsequently, palatal tissues from E13.5 embryos were treated with varying concentrations of Midline1 small interfering RNA (MID1 siRNA), and the knockdown efficiency was evaluated using Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR), with each concentration tested in triplicate. Based on the results, the most effective concentration, 100 nM MID1 siRNA, was selected for further experiments. Subsequently, twelve E13.5 palatal explants were allocated into two groups: six explants were treated with 100 nM MID1 siRNA (experimental group), and six with scrambled small interfering RNA(Scramble siRNA; control group). After 48 h of in vitro culture, hematoxylin and eosin (HE) staining was performed to evaluate the morphology of palatal shelf fusion. To evaluate apoptotic activity, Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) staining was performed on both experimental and control groups. Finally, immunohistochemistry and Western blot analyses were conducted to examine the expression levels of Matrix Metalloproteinase 8 (MMP8) and Snail Family Transcription Factors (Snail) proteins in three biological replicates from each group.

Results

Midline1 deficiency resulted in incomplete palatal shelf fusion and significantly reduced apoptosis. Additionally, the knockdown of Midline1 led to the upregulation of Snail and MMP8 gene expression, indicating that Midline1 plays a critical role in regulating epithelial-to-mesenchymal transition and maintaining cytoskeletal stability during palate development.

Conclusions

Midline1 is essential for normal secondary palate development. Its dysregulation disrupts palatal shelf fusion and morphology, potentially contributing to craniofacial abnormalities such as cleft palate. These findings provide new insights into the molecular mechanisms underlying palate development and suggest that Midline1 could be a therapeutic target for addressing cleft palate and related defects.