Regarding a kingdom extension HH (Hedgehugs)

[ven]

It's funny that the OP uses that abbreviation because HH is the name of a protein group called "hedgehog". That protein is produced by the Sonic Hedgehog gene (SHH), and it's also called Sonic Hedgehog Protein Preproprotein.

True story
https://ghr.nlm.nih.gov/gene/SHH

[Flyrella]

It's funny that the OP uses that abbreviation because HH is the name of a protein group called "hedgehog". That protein is produced by the Sonic Hedgehog gene (SHH), and it's also called Sonic Hedgehog Protein Preproprotein.

True story
https://ghr.nlm.nih.gov/gene/SHH

Genes should be written with italic