Vomeromodulin is a non-human protein also known as BPI fold containing family B, member 9 (BPIFB9) in the rat encoded by the ''Bpifb9/RYF3'' gene, and as BPI fold containing family B, member 9A (BPIFB9A) encoded by the ''Bpifb9a'' gene in the mouse. This protein has been characterized in mammals such as

rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are nat ...

, carnivores, even-toed ungulates,

insectivores A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores wer ...

bats Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...

lagomorphs The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae ( hares and rabbits) and the Ochotonidae (pikas). The name of the order is derived from the Ancient Greek ''lagos'' (λα� ...

, and shrews but is apparently absent in primates and other vertebrates such as birds, reptiles, and amphibians. Its function is associated with detection of chemical odorant pheromone molecules. In humans no protein is expressed and it is present only as a

pseudogene Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, either directly by DNA duplication or indirectly by Reverse transcriptase, reverse transcription of an mRNA trans ...

''BPIFB9P''. The pseudogene was named based on its functional ortholog found in the other species.

Superfamily

Vomeromodulin/BPIFB9/BPIFB9A is a member of the BPI fold

protein superfamily A protein superfamily is the largest grouping (clade) of proteins for which common ancestry can be inferred (see homology (biology), homology). Usually this common ancestry is inferred from structural alignment and mechanistic similarity, even if n ...

defined by the presence of the bactericidal/permeability-increasing protein fold (BPI fold) which is formed by two similar domains in a "boomerang" shape.This superfamily is also known as the BPI/LBP/PLUNC family or the BPI/ LPB/ CETP family. The BPI fold creates apolar binding pockets that can interact with hydrophobic and amphipathic molecules, such as the acyl carbon chains of lipopolysaccharide found on Gram-negative bacteria, but members of this family may have many other functions. BPIFfamily-BPIFB9P

Genes for the BPI/LBP/PLUNC superfamily are found in all vertebrate species, including distant homologs in non-vertebrate species such as insects, mollusks, and roundworms. Within that broad grouping is the BPIF gene family whose members encode the BPI fold

structural motif In a polymer, chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a common Biomolecular structure#Tertiary structure, three-dimensional structure that appears in a variety of different, evolutionarily unrel ...

and are found clustered on a single chromosome, e.g., Chromosome 20 in humans, Chromosome 2 in mouse, Chromosome 3 in rat, Chromosome 17 in pig, Chromosome 13 in cow. The BPIF gene family is split into two groupings, BPIFA (SPLUNC) and BPIFB (LPLUNC). In humans, BIPFA consists of 3 protein encoding genes ''

BPIFA1 BPI fold containing family A, member 1 (BPIFA1), also known as Palate, lung, and nasal epithelium clone (PLUNC), is a protein that in humans is encoded by the ''BPIFA1'' gene. It was also formerly known as "Secretory protein in upper respiratory ...

'', '' BPIFA2'', '' BPIFA3'', and 1 pseudogene '' BPIFA4P''; while BPIFB consists of 5 protein encoding genes '' BPIFB1'', '' BPIFB2'', '' BPIFB3'', '' BPIFB4'', '' BPIFB6'' and 2 pseudogenes '' BPIFB5P'', ''BPIFB9P''. What appears as pseudogenes in humans may appear as fully functional genes in other species. The ''PIFB9P'' pseduogene in humans was first reported in 2011 as a member of the BPI/LBP/PLUNC family, but clones containing ''PIFB9P'' had been detected in 1999 genomic screening by the Welcome Trust Sanger Institute.

Function

In humans, the expression of the ''BPIFB9P'' pseudogene into functional BPIFB9 protein is unclear. Although identified multiple times by independent scientists as a pseudogene not capable of coding for a protein, its gene sequence may predict two transcripts ( splice variants) and RNA transcripts detected by

RNA-Seq RNA-Seq (named as an abbreviation of RNA sequencing) is a sequencing technique which uses next-generation sequencing (NGS) to reveal the presence and quantity of RNA in a biological sample at a given moment, analyzing the continuously changing c ...

screens have been observed in brain tissues, striated muscle, white blood cells ( granulocytes,

monocytes Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and conventional dendritic cells. As a part of the vertebrate innate immune system monocytes also infl ...

), and esophageal

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

. Yet, definitive evidence for human BPIFB9 protein has never been produced and is unlikely to happen. The non-human version of this protein, however, is well known. Vomeromodulin is highly expressed in nasal mucosa, particularly within a structure known as the Vomeronasal organ. The vomeronasal organ is present and well-developed in many mammals to process pheromone odors into neural signals to the brain, but the chemical and neural components of the vomeronasal system have been completely inactivated in most primates, including humans. In this context, BPIFB9-type proteins are thought to be similar to odorant binding proteins which presents odorant molecules to chemical odorant receptor molecules. Those odorant receptors, in turn, are associated with nasal epithelial cells integrated with olfactory neurons that project back to the brain's oflactory areas and hypothalamus. It has been established that the genes and proteins for these components are present and active in many mammal species, but in higher primates the genes are found to be mutated and appear as non-functional pseudogenes, like ''BPIFB9P''.

References

External links

* {{UCSC gene info, BPIFB9P Pseudogenes Genes on human chromosome 20