Transcription factor Sp8 also known as specificity protein 8 (SP-8) or Btd transcription factor (buttonhead) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

that in humans is encoded by the ''SP8''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. Sp8 is a

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...

in the Sp/KLF family.

Function

Sp8 mediates limb outgrowth during early development. Sp8 deletion in mice resulted in severe

exencephaly Exencephaly is a type of cephalic disorder wherein the brain is located outside of the skull. This condition is usually found in embryos as an early stage of anencephaly. As an exencephalic pregnancy progresses, the neural tissue gradually degenerat ...

. Sp8 is a zinc-finger transcription factor. The structural difference between Sp8 and Sp9 is only one amino acid. These transcription factors are Apical Ectodermal Ridge (AER) specific in limb development. The Apical Ectodermal Ridge signaling is important for specification of distal limb structures. Sp8 and Sp9 mediate Fgf10 signaling, which in turn regulates Fgf8 expression (Fgf10--->Fgf8). Fgf8 is essential for normal limb development, and without the presence of Fgf8 in early development, there would be a decreased length of the limb bud and possible failure of the limb tissue develop. Both Sp8 and Sp9 have been found in vertebrates. Although, so far only Sp8 has been proven to be present in invertebrates too. Under lab conditions, Sp8 replaced btd in Drosophila, showing that Sp8 and btd both have similar functions in limb development in both vertebrates and invertebrates. Gene knockdown in zebrafish displayed that Fgf8 expression is necessary for appendage development.

Function

References

Further reading