ABSTRACT
Objective: To investigate the effect of the trace element zinc (Zn) on apoptosis and cell proliferation in palate shelvesduring the fusion phase, and to screen candidate genes of the Zn-finger special protein (Sp) family that were differentially expressed between the cleft palate and the normal palate to explore the mechanism of Zn in the development of cleft palate. Methods: Zn-rich, normal-Zn, low-Zn, and Zn-deficient diets were fed to female mice and, for the resultant fetuses, paraffin slices of their heads were made at embryonicdays 14.5 and 16.5. Using terminaldeoxynucleotidyltransferase-mediated dUTP nick-end labeling, the number of apoptotic cells in the palatal shelves was counted, and cell proliferation activity was detected using proliferating cell nuclear antigen staining. Total RNA from the palatal shelves of fetal mice was extracted from the Zn-rich diet, normal Zn-diet, and Zn-deficient-diet groups. We used microarray analysis to examine the expression of genes to identify intergroup differential gene expression and polymerase chain reaction tests to validate the results. Results: At ED14.5, the incidence of cleft palate in the regular zinc group, zinc rich group, low zinc group, and zinc deficient group was 8% (3/36), 2% (1/39), 29% (12/41), and 39% (15/38), respectively. The HE staining results at ED14.5 showed that both the left and right palatal processes in the zinc group had been lifted up and were in contact and connected with each other. In the zinc deficiency group, the left and right palatine processes remained vertically downwards on both sides of the tongue, ultimately forming cleft palate; In the low zinc group, the left and right palatine processes were raised but not in contact, ultimately resulting in cleft palate. There is no significant difference between the zinc rich group and the regular zinc group. At ED14.5, the positive rates of proliferative cells in the palatal process of fetal mice in the regular zinc group (80.29% ± 7.39%) and the zinc rich group (87.69% ± 6.62%) were significantly higher than those in the zinc deficient group (56.05% ± 16.13%) and the low zinc group (56.22% ± 9.61%) (t=4.32, P<0.05). The apoptosis index of fetal rat palatal process cells in the zinc deficient group (38.80% ± 3.10%) and the low zinc group (28.80% ± 6.19%) were significantly higher than those in the regular zinc group (16.80% ± 1.82%) (t=19.35, P<0.001; t=5.81, P<0.001). There were 663 differentially expressed genes in the zinc rich group and the zinc deficient group, with 513 up-regulated genes and 150 down-regulated genes, among which Sp5 was found to be located. The real time PCR results showed that compared with the regular zinc group (2.22 ± 0.36), the expression level of Sp5mRNA in the palatal process tissue of the zinc deficient group (1.23 ± 0.38) significantly increased (P<0.05), while the zinc rich group (3.68 ± 0.90) significantly decreased (P<0.05). Conclusions: Trace element Zn content was found to be closely related to the occurrence of cleft palate in mice offspring, with a lack of Zn leading to cleft palate.
