An unexpected finding has emerged from the molecular biology laboratory at Tokushima University, Japan. drg. Ivan Arie Wahyudi, M.Kes., Ph.D., and his research team discovered that the Sp6 gene, known as an important regulator of tooth development in mice, has not just one but three distinct promoter regions. One of them was found in a completely unexpected location: inside an intron, a segment of DNA traditionally regarded as a \u201cnon-coding\u201d region. The research was published in The Indonesian Journal of Dental Research in 2010, making it one of the early contributions by Indonesian scientists to the mapping of the genetic mechanisms underlying tooth development.<\/p>\n\n\n\n
To understand why this finding matters, it is useful to start with the basics. The development of every tooth in the mouth is far from a simple process. It involves complex communication between two layers of tissue: the dental epithelium, the outer layer that will eventually form tooth enamel, and the mesenchyme, the inner tissue that forms dentin and pulp. These two tissues communicate with one another through molecular signals.<\/p>\n\n\n\n
At the center of this molecular conversation, the Sp6 gene serves as one of the key coordinators. The gene produces the SP6 protein, a member of the SP\/Kr\u00fcppel-like family of transcription factors. Mice lacking the Sp6 gene exhibit abnormalities in their teeth, hair, and limb buds. In an earlier study, the same research team also found that overexpression of Sp6 in ameloblasts\u2014the cells responsible for producing tooth enamel\u2014suppressed expression of the follistatin gene, indicating that Sp6 has specific targets during enamel development.<\/p>\n\n\n\n
However, a more fundamental question remained unanswered: how is Sp6 expression itself regulated? This is where the study by drg. Ivan and his team comes in.<\/p>\n\n\n\n
The researchers used 5\u2032 RACE (Rapid Amplification of cDNA Ends) on RNA extracted from the mandibles of 18.5-day-old mouse embryos. The results were surprising. They identified two different transcription start ends in Sp6 transcripts, which were subsequently designated exon 1a and exon 1b, each controlled by a different promoter\u2014the first and second promoters, respectively.<\/p>\n\n\n\n
What made the finding particularly interesting was the difference in activity between the two promoters. When tested using a luciferase reporter assay\u2014a standard method for measuring gene promoter activity in which greater luminescence indicates stronger promoter activity\u2014the first promoter produced only weak activity. By contrast, the second promoter showed much stronger activity, reaching 82\u2013129 times that of the control, particularly in dental epithelial cells.<\/p>\n\n\n\n
\u201cOur findings may provide new insights into the mechanisms regulating Sp6 gene expression and link cytokine regulation to inductive interactions between the epithelium and mesenchyme.\u201d \u2014 drg. Ivan Arie Wahyudi, M.Kes., Ph.D., and colleagues<\/em><\/p>\n\n\n\n Then came an unexpected discovery. When the team analyzed intron 2, a DNA region conventionally regarded as inactive in protein coding, they detected significant promoter activity. A construct containing only the intron 2 region still demonstrated approximately 110-fold activity, roughly one-third of the highest promoter activity measured. This led the researchers to identify it as a potential third promoter.<\/p>\n\n\n\n The findings did not stop at mapping the promoters. The team also investigated how two key signaling molecules involved in tooth development\u2014BMP2 (bone morphogenetic protein 2) and Wnt1 (wingless)\u2014affected Sp6 promoter activity.<\/p>\n\n\n\n The results provided an increasingly complex picture. BMP2 treatment of G5 cells increased Sp6 mRNA levels by up to sixfold, while Wnt1 increased them by approximately 2.5-fold. More interestingly, the response to BMP2 was detected only in constructs containing the third promoter, whereas Wnt1 affected both the second and third promoters. This suggests that each promoter has a different degree of sensitivity to signals originating outside the cell.<\/p>\n\n\n\n These findings strengthen the direct connection between the BMP and Wnt signaling pathways, which have long been recognized as key players in epithelial\u2013mesenchymal interactions, and the regulation of Sp6 transcription during tooth development.<\/p>\n\n\n\n The research was not yet completely conclusive. The team acknowledged that definitive confirmation of the third promoter requires identification of the precise transcription start sites, an issue that remains for future research. The question of why the first promoter showed weak activity in dental epithelial cells also remains unresolved, with several possible explanations ranging from the epigenetic status of the cells to the absence of specific transcription factors such as Ctip2\/Bcl11b.<\/p>\n\n\n\n Nevertheless, the contribution of this research is already clear. The regulatory map of Sp6 generated by the study provides a pathway toward understanding why developmental abnormalities of the teeth occur at the molecular level. Ultimately, understanding how genes \u201cswitch themselves on and off\u201d during tooth development forms a foundation for future regenerative dentistry, in which one day missing teeth may potentially be regenerated not from artificial materials, but from the body\u2019s own genetic instructions.<\/p>\n\n\n\n Authors: Achmad Zam Zam Aghasy, DDS, M.Kes.; Hazra Alifia Muharam<\/p>\n\n\n\n Photo: Freepik<\/p>\n\n\n\n <\/p>","protected":false},"excerpt":{"rendered":" Sebuah temuan tak terduga muncul dari laboratorium biologi molekuler di Universitas Tokushima, Jepang. drg. Ivan Arie Wahyudi, M.Kes., Ph.D., bersama tim penelitinya, berhasil mengungkap bahwa gen Sp6, yang dikenal sebagai pengatur penting dalam proses pembentukan gigi pada tikus, ternyata memiliki tidak hanya satu, melainkan tiga wilayah promoter yang berbeda. Salah satunya ditemukan di lokasi yang […]<\/p>\n","protected":false},"author":615,"featured_media":20610,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[359,136],"tags":[307,289,291,297],"class_list":["post-20604","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-artikel","category-berita-terbaru","tag-sdg-17-kemitraan-untuk-mencapai-tujuan","tag-sdg-3-kesehatan-dan-kesejahteraan-yang-baik","tag-sdg-4-pendidikan-berkualitas","tag-sdg-9-industri-inovasi-dan-infrastruktur"],"gutentor_comment":0,"yoast_head":"\nBMP and Wnt Signals: External Amplifiers<\/h2>\n\n\n\n
A New Window into Dental Biology<\/h2>\n\n\n\n