The Flatworm Macrostomum lignano Is a Powerful Model Organism for Ion Channel and Stem Cell Research

Table 2

Major categories of ion channel genes conserved between H. sapiens and M. lignano.

GO term	Description	𝐻	𝑀	Human genes
GO:0004889	Acetylcholine-activated cation-selective channel activity	13	132	CHRNA4, CHRNE, CHRNA10, CHRNB1, CHRNB3, CHRNA6, CHRNA3, CHRND, CHRNB2, CHRNB4, CHRNA9, CHRNA2, CHRNA7
GO:0004931	Extracellular ATP-gated cation channel activity	5	15	P2RX6, P2RX7, P2RX5, P2RX4, P2RX2
GO:0004970	Ionotropic glutamate receptor activity	12	67	GRIN1, GRIA4, GRIN2A, GRIK2, GRIK1, GRIA1, GRIK4, GRIA2, GRIK3, GRID1, GRIN3A, GRIK5
GO:0005216	Ion channel activity	6	23	PKD1L2, MCOLN3, MCOLN2, PKD2L2, PKD2L1, PKDREJ
GO:0005221	Intracellular cyclic nucleotide activated cation channel activity	2	5	KCNA10, CNGA3
GO:0005222	Intracellular cAMP activated cation channel activity	1	2	HCN4
GO:0005223	Intracellular cGMP activated cation channel activity	1	1	CNGB3
GO:0005229	Intracellular calcium activated chloride channel activity	2	3	ANO1, ANO2
GO:0005232	Serotonin-activated cation-selective channel activity	2	3	HTR3B, HTR3A
GO:0005237	Inhibitory extracellular ligand-gated ion channel activity	2	3	GABRA6, GABRB2
GO:0005242	Inward rectifier potassium channel activity	6	26	KCNH6, KCNJ12, KCNK6, KCNJ8, KCNQ5, KCNH7
GO:0005245	Voltage-gated calcium channel activity	8	27	CACNA1C, CATSPER1, CACNG7, CACNG5, CACNB1, CACNA1B, CACNB2, CACNA1E
GO:0005247	Voltage-gated chloride channel activity	6	14	CLCN7, CLCN4, CLIC1, CLIC4, CLIC6, CLCN3
GO:0005248	Voltage-gated sodium channel activity	8	19	SCN3A, SCN2A, SCN4A, PKD2, SCN8A, SCN5A, SCN9A, SCN11A
GO:0005249	Voltage-gated potassium channel activity	23	75	KCTD12, KCTD21, KCNH3, KCTD10, KCTD3, KCTD6, KCNAB3, KCTD2, KCTD15, KCTD7, KCNH4, KCNB1, KCTD9, KCNH8, KCNC3, KCNC2, KCTD16, KCND1, KCNC1, KCNV2, KCNH5, KCTD1, KCTD20
GO:0005250	A-type (transient outward) potassium channel activity	3	11	KCNIP2, KCND3, KCND2
GO:0005251	Delayed rectifier potassium channel activity	8	26	KCNA3, KCNB2, KCNH2, KCNA1, KCNA5, KCNQ1, KCNA2, KCNH1
GO:0005254	Chloride channel activity	17	55	CLCA1, ANO3, GABRB3, GABRA2, GABRB1, ANO7, ANO9, ANO4, GABRG2, CLCA4, CLCC1, ANO6, GABRQ, GABRG1, ANO10, GABRA4, GABRG3
GO:0005261	Cation channel activity	7	33	TRPM3, TRPV4, TRPM6, TRPC7, TMEM38A, TRPV1, HCN2
GO:0005262	Calcium channel activity	7	51	TRPM1, TRPM7, TRPM8, TRPV5, TRPM5, TRPM4, TRPV6
GO:0005267	Potassium channel activity	13	27	KCNC4, KCNK16, KCNK10, KCNG1, KCNK2, KCNK5, KCNK3, KCNK12, KCNQ4, KCNK17, KCNIP1, KCNIP4, KCNK9
GO:0005272	Sodium channel activity	4	40	HCN1, NALCN, ACCN4, TRPM2
GO:0008308	Voltage-gated anion channel activity	2	3	VDAC1, VDAC2
GO:0008331	High voltage-gated calcium channel activity	7	38	CACNA1A, CACNA2D4, CACNA1D, CACNA2D1, CACNA1S, CACNA2D3, CACNA2D2
GO:0008332	Low voltage-gated calcium channel activity	3	18	CACNA1H, CACNA1I, CACNA1G
GO:0015269	Calcium-activated potassium channel activity	9	49	KCNMA1, KCNN1, KCNT2, KCNN2, KCNT1, KCNU1, KCNMB2, KCNK18, KCNN3
GO:0015276	Ligand-gated ion channel activity	2	4	CLCA2, CNGB1
GO:0015279	Store-operated calcium channel activity	5	40	TRPC4, TRPC6, ORAI1, TRPA1, TRPC3
GO:0015280	Ligand-gated sodium channel activity	8	97	SCNN1B, SCNN1G, ACCN1, ACCN3, SCNN1A, ACCN5, ACCN2, SCNN1D
GO:0022824	Transmitter-gated ion channel activity	4	34	GLRA2, GLRA4, GLRA1, GLRA3
GO:0030171	Voltage-gated proton channel activity	1	3	HVCN1
GO:0072345	NAADP-sensitive calcium-release channel activity	2	3	TPCN1, TPCN2
	Total	199	947
	Total number of genes in these GO categories	390

𝐻: number of different ion channel genes in human with homologs in M. lignano. 𝑀: number of transcripts in M. lignano de novo transcriptome assembly ML110815 with homology to ion channel genes in human. Note that alternatively spliced transcripts are counted separately in the M. lignano transcriptome assembly, hence the total reported number of transcripts is higher than the number of corresponding human genes. For this classification, genes were assigned to the least frequent available GO term within predefined list of ion channel-related GO terms (molecular function domain).