FAM199X

FAM199X, also known as CXorf39, is a gene located on the X chromosome that encodes a protein known as FAM199X.^[1] This gene is expressed in most vertebrates, including most mammals, birds, amphibians, and fish.^[2] Within humans, this gene is commonly expressed in the brain and thyroid.^[2] The gene has been linked to some genetic disorders, such as Pelizaeus–Merzbacher disease, and some cancers, such as Stomach cancer, but FAM199X's role in those diseases is not yet well understood within the scientific community.^[3]

Location of FAM199X on the X chromosome.

Molecular entity

Gene

FAM199X, also known as CXorf39, is located on the long arm of the X chromosome at Xq22.2 on the plus strand between bases 104,166,453 and 104,195,902 and encodes six exons.^[1][3] The gene is located next to an enhancer called LOC130068517, also known as ATAC-STARR-Seq Lymphoblastoid Active Region 29826.^[4]

Transcript

Four transcript variants of FAM199X produce two protein isoforms. The four transcript variants are FAM199X-X1 with 7498 nucleotides, FAM199X-X1 with 7495 nucleotides, FAM199X-X2 with 7179 nucleotides, and FAM199X-X1 with 7171 nucleotides.^[5] There are six exons in FAM199X-X1 variants and five exons in FAM199X-X2 variants.^[1]

FAM199X has two isoforms, each with 6 exons and two variants of each isoform. Isoform x1 encodes for 345 amino acids while Isoform x2 encodes a 205 amino acid protein.^[6]

Isoform Table

Transcript Variant	Accession # mRNA	Length (nt)	Exons	Protein isoform	Accession # Protein	Length (aa)	Isoelectric Point (pI)
Variant 1	XM_005262079.4	7495	6	Isoform X1	XP_005262136.1	345	4.84
Variant 2	XM_054326467.1	7498	6	Isoform X1	XP_054182442.1	345	4.84
Variant 3	XM_047441826.1	7179	6	Isoform X2	XP_047297782.1	205	9.07
Variant 4	XM_054326468.1	7171	6	Isoform X2	XP_054182443.1	205	9.07

Protein

There are two protein isoforms of FAM199X, FAM199X-X1 and FAM199X-X2.^[7] FAM199X-X1 is 345 amino acids long and 38.61kDa, and FAM199X-X2 is 205 amino acids long and 22.8kDa.^[7][8]

Homologs

FAM199X had several highly conserved orthologs amongst mammals, birds, reptiles, amphibians, fish, and less conserved orthologs in chorodates and arachnids. The most distant ortholog detected is the Common Household Spider, Parasteatoda tepidaiorum.

Paralogs

FAM199X has no paralogs.

Evolution

FAM199X evolved around 708 million years ago, with the oldest known ortholog, Parasteatoda tepidaiorum, diverging from human evolution about 708 million years ago.

Orthologs

Genus and Species	Common name	Taxonomy	Date of divergence (MYA)	Accession #	Sequence length (aa)	Identity (%)	Similarity (%)
Homo sapiens	Human	Primates	0	NM_207318.4	388	100	100
Macaca mulatta	Indochinese rhesus macaque		28.8	NP_001180862.1	388	100	100
Plecturocebus cupreus	Coppery titi monkey		43	KAL0588686.1	423	99	100
Mus musculus	House mouse	Mammal	87	NP_666373.1	388	98	97
Pteropus vampyrus	Large flying fox		94	XP_011379288.1	388	99	99
Ornithorhynchus anatinus	Platypus		180	XP_028923647.1	390	93	95
Chelydra serpentina	Common snapping turtle	Reptiles	319	KAG6937128.1	381	90	92
Eublepharis macularius	Leopard gecko		319	XP_054853091.1	384	87	89
Gallus gallus	Red junglefowl	Birds	319	XP_003641135.2	381	90	92
Ranitomeya variabilis	Zimmerman's poison frog	Amphibian	352	XP_077141317.1	375	89	92
Erpetoichthys calabaricus	Reedfish	Fish	429	XP_028671530.1	377	85	89
Collichthys lucidus	Spinyhead Croaker		429	TKS72713.1	396	78	83
Leucoraja erinaceus	Little skate		462	XP_055499985.1	378	81	86
Pristis pectinata	Smalltooth sawfish		462	XP_051876775.1	378	81	86
Lethenteron reissneri	Asiatic Brook Lamprey	Jawless Vertebrate	563	XP_061419915.1	441	59	69
Branchiostoma lanceolatum	Common lancelet	Invertebrate	581	CAH1254916.1	356	33	51
Nematostella vectensis	Starlet Sea Anemone		685	XP_001632934.1	344	31	44
Ixodes scapularis	Deerk tick		686		353	31	49
Magallana gigas	Pacific Oyster		708	XP_011447698.3	317	30	47
Parasteatoda tepidariorum	Common house spider		708	XP_042905439.1	273	28	44