EPPIN

Summary

EPPIN (epididymal peptidase inhibitor, HGNC:15932) is a protein-coding gene on chromosome 20q13.12, encoding Eppin (O95925). Serine protease inhibitor that plays an essential role in male reproduction and fertility.

This gene encodes an epididymal protease inhibitor, which contains both kunitz-type and WAP-type four-disulfide core (WFDC) protease inhibitor consensus sequences. Most WFDC genes are localized to chromosome 20q12-q13 in two clusters: centromeric and telomeric. This gene is a member of the WFDC gene family and belongs to the telomeric cluster. The protein can inhibit human sperm motility and exhibits antimicrobial activity against E. coli, and polymorphisms in this gene are associated with male infertility. Read-through transcription also exists between this gene and the downstream WFDC6 (WAP four-disulfide core domain 6) gene. Two transcript variants encoding different isoforms have been found for this gene.

Source: NCBI Gene 57119 — RefSeq curated summary.

At a glance

• Clinical variants (ClinVar): 1 total
• MANE Select transcript: NM_020398

Identifiers

Gene identifiers

Field	Value
HGNC ID	HGNC:15932
Approved symbol	EPPIN
Name	epididymal peptidase inhibitor
Location	20q13.12
Locus type	gene with protein product
Status	Approved
Aliases	EPPIN1, EPPIN2, EPPIN3, dJ461P17.2, WAP7, WFDC7, CT71
Ensembl gene	ENSG00000101448
Ensembl biotype	protein_coding
OMIM	609031
Entrez	57119

Gene structure

Transcript identifiers

Ensembl transcripts: 4 — 3 protein_coding, 1 retained_intron

ENST00000336443, ENST00000354280, ENST00000409554, ENST00000496898

RefSeq mRNA: 2 — MANE Select: NM_020398 NM_001302861, NM_020398

CCDS: CCDS13359

Canonical transcript exons

ENST00000354280 — 4 exons

Exon	Start	End
ENSE00001290879	45540626	45542154
ENSE00001885325	45547267	45547401
ENSE00003560863	45542700	45542867
ENSE00003676714	45545639	45545770

Expression profiles

Bgee: expression breadth broad, 96 present calls, max score 96.98.

FANTOM5 (CAGE): breadth tissue_specific, TPM avg 0.0115 / max 8.8046, expressed in 3 samples.

FANTOM5 promoters (4 alternative TSS)

Promoter ID	TPM avg	Samples expressed
187452	0.2667	5
187453	0.0203	4
187455	0.0073	3
187456	0.0042	2

Top tissues by expression

218 total, by Bgee expression score (0-100, higher = more expressed):

Tissue	Anatomy ID	Expression score	Quality
right testis	UBERON:0004534	96.98	gold quality
corpus epididymis	UBERON:0004359	96.22	gold quality
left testis	UBERON:0004533	96.04	gold quality
buccal mucosa cell	CL:0002336	94.32	gold quality
testis	UBERON:0000473	93.50	gold quality
adult organism	UBERON:0007023	93.44	gold quality
epithelium of bronchus	UBERON:0002031	85.43	gold quality
bronchus	UBERON:0002185	84.28	gold quality
bronchial epithelial cell	CL:0002328	83.95	gold quality
cauda epididymis	UBERON:0004360	82.19	gold quality
mucosa of paranasal sinus	UBERON:0005030	81.84	gold quality
olfactory segment of nasal mucosa	UBERON:0005386	80.63	gold quality
primordial germ cell in gonad	CL:0000670 ∩ UBERON:0000991	79.20	silver quality
male germ line stem cell (sensu Vertebrata) in testis	CL:0000089 ∩ UBERON:0000473	77.91	gold quality
right uterine tube	UBERON:0001302	77.32	gold quality
nasal cavity epithelium	UBERON:0005384	73.79	gold quality
caput epididymis	UBERON:0004358	68.97	gold quality
nasal cavity mucosa	UBERON:0001826	66.50	gold quality
epithelium of nasopharynx	UBERON:0001951	65.77	silver quality
male germ cell	CL:0000015	63.17	silver quality
sperm	CL:0000019	59.78	silver quality
oviduct epithelium	UBERON:0004804	57.78	silver quality
upper leg skin	UBERON:0004262	57.36	gold quality
fallopian tube	UBERON:0003889	56.90	gold quality
tibialis anterior	UBERON:0001385	56.77	silver quality
ileal mucosa	UBERON:0000331	56.36	silver quality
left lobe of thyroid gland	UBERON:0001120	55.16	gold quality
right lung	UBERON:0002167	54.88	gold quality
cranial nerve II	UBERON:0000941	54.73	gold quality
thyroid gland	UBERON:0002046	53.72	gold quality

Single-cell (SCXA)

Detected in 2 experiment(s), a significant marker in 2.

Experiment	Marker?	Max mean expression
E-GEOD-134144	yes	487.60
E-ANND-3	yes	9.08

Regulation

Is transcription factor: no

Upstream regulators (CollecTRI, top): ATRX, ESR1

miRNA regulators (miRDB)

31 targeting EPPIN, top 30 by miRDB confidence (max_score; target_count = how many genes the miRNA targets in total — lower means more specific):

miRNA	Max score	Avg score	miRNA target_count
HSA-MIR-3134	100.00	66.43	777
HSA-MIR-4500	99.99	72.72	2367
HSA-MIR-4534	99.99	66.58	1907
HSA-MIR-4531	99.99	69.70	3181
HSA-LET-7A-5P	99.98	72.29	1790
HSA-LET-7B-5P	99.98	72.31	1790
HSA-LET-7C-5P	99.98	72.29	1790
HSA-LET-7E-5P	99.98	72.29	1790
HSA-LET-7F-5P	99.98	72.56	1784
HSA-LET-7G-5P	99.98	72.37	1784
HSA-LET-7I-5P	99.98	72.37	1788
HSA-MIR-98-5P	99.98	72.33	1787
HSA-MIR-3148	99.97	75.06	6478
HSA-LET-7D-5P	99.96	71.76	1632
HSA-MIR-4458	99.96	71.64	1650
HSA-MIR-1825	99.72	68.11	1089
HSA-MIR-875-3P	99.63	69.47	2548
HSA-MIR-671-5P	99.52	67.11	1277
HSA-MIR-766-5P	99.47	67.91	2225
HSA-MIR-4426	99.17	66.74	1949
HSA-MIR-6868-5P	99.06	65.69	1284
HSA-MIR-4738-3P	98.98	67.98	1846
HSA-MIR-10526-3P	97.86	64.97	1342
HSA-MIR-4314	97.50	67.30	1369
HSA-MIR-3192-5P	96.98	65.76	1926
HSA-MIR-1270	96.94	66.65	931
HSA-MIR-620	96.94	66.79	888
HSA-MIR-12128	96.67	66.98	1471
HSA-MIR-1236-5P	96.62	66.38	856
HSA-MIR-5586-3P	95.51	67.00	805

Literature-anchored findings (GeneRIF, showing 14)

• This antimicrobial peptide permeabilized outer and inner membranes of E. coli, consistent with its ability to induce striking morphological alterations of E. coli membranes. Has role in innate immune system of human epididymis. (PMID:15229136)
• in seminal plasma and on spermatozoa following ejaculation, Eppin is bound to semenogelin I (PMID:15590901)
• although both of eppin’s domains are involved in the protein’s antibacterial activity, only the Kunitz domain is required for selective protease inhibition (PMID:18331357)
• Eppin protects a 15-kDa fragment of semenogelin from hydrolysis by prostate specific antigen (PMID:18645681)
• Eppin can modulate intracellular calcium concentrations and subsequently affect the calcium ionophore A23187-induced acrosome reaction. (PMID:19801569)
• Cysteine 239 of rSEMG1 appears to be the critical amino acid for both binding to eppin and inhibiting sperm motility. (PMID:19889947)
• Genetic variants in the Eppin gene may be associated with semen quality. (PMID:20158997)
• Different variants in the EPPIN gene are related to idiopathic male infertility and men carrying these variants have a decreased or increased risk of abnormal semen parameters associated with male infertility. (PMID:20488803)
• Letter: Eppin overexpression in prostate cancer correlates with favorable prognosis. (PMID:21392882)
• The expression of mouse EPPIN protein was detected in A1-A4 spermatogonia and the expression of human EPPIN was detected in type A spermatogonia as well as in the earliest preleptotene spermatocytes. (PMID:21461566)
• EPPIN’s semenogelin I binding site: a contraceptive drug target. (PMID:22699487)
• EPPIN and SEMG1 rapidly co-evolved in primates (PMID:24312623)
• Eppin and Fibronectin bind to each other in human semen and on human ejaculated spermatozoa. (PMID:24358212)
• eppin plays a role outside of the reproductive tract; eppin may have a role in the innate immune response in the lung (PMID:28705940)

Cross-species orthologs

16 orthologs

Organism	Symbol	Gene ID
danio_rerio	spint1b	ENSDARG00000012467
danio_rerio	lrp11	ENSDARG00000034076
danio_rerio	wfikkn1	ENSDARG00000101364
danio_rerio	spint1a	ENSDARG00000102332
mus_musculus	Eppin	ENSMUSG00000017733
rattus_norvegicus	Eppin	ENSRNOG00000028908
drosophila_melanogaster	CG7565	FBGN0035833
caenorhabditis_elegans		WBGENE00008304
caenorhabditis_elegans		WBGENE00008449
caenorhabditis_elegans		WBGENE00009386
caenorhabditis_elegans		WBGENE00010792
caenorhabditis_elegans		WBGENE00012186
caenorhabditis_elegans		WBGENE00012814
caenorhabditis_elegans		WBGENE00015355
caenorhabditis_elegans		WBGENE00020648
caenorhabditis_elegans		WBGENE00021939

Paralogs (13): TFPI (ENSG00000003436), TFPI2 (ENSG00000105825), AMBP (ENSG00000106927), LRP11 (ENSG00000120256), WFIKKN1 (ENSG00000127578), KIAA0319 (ENSG00000137261), KIAA0319L (ENSG00000142687), SPINT4 (ENSG00000149651), WFDC8 (ENSG00000158901), SPINT1 (ENSG00000166145), SPINT2 (ENSG00000167642), WFIKKN2 (ENSG00000173714), WFDC6 (ENSG00000243543)

Protein

Protein identifiers

Eppin — O95925 (reviewed: O95925)

Alternative names: Cancer/testis antigen 71, Epididymal protease inhibitor, Protease inhibitor WAP7, Serine protease inhibitor-like with Kunitz and WAP domains 1, WAP four-disulfide core domain protein 7

All UniProt accessions (3): O95925, A0A384NYB9, B7ZBA9

UniProt curated annotations — full annotation on UniProt →

Function. Serine protease inhibitor that plays an essential role in male reproduction and fertility. Modulates the hydrolysis of SEMG1 by KLK3/PSA (a serine protease), provides antimicrobial protection for spermatozoa in the ejaculate coagulum, and binds SEMG1 thereby inhibiting sperm motility.

Subunit / interactions. Monomer. Homodimer. Homomultimers. Interacts with SEMG1 (via 164-283 AA). Interacts with LTF. Found in a complex with LTF, CLU, EPPIN and SEMG1.

Subcellular location. Secreted. Cell surface.

Tissue specificity. In testis, expressed and secreted by Sertoli cells, appearing on the surface of testicular and ejaculate spermatozoa. Expressed in the spermatogonia and the earliest preleptotene spermatocytes. In the epididymis, is expressed and secreted by epithelial cells and covers the surface of epididymal spermatozoa and ciliated epithelial cells (at protein level). Expressed specifically in epididymis and testis. Isoform 2 is expressed only in the epididymis. Weak expression is detected in myoid cells as well as spermatogenic cells.

Domain organisation. The BPTI/Kunitz inhibitor domain is required for elastase inhibitory activity. BPTI/Kunitz inhibitor and WAP domains are involved in the protein antibacterial activity.

Miscellaneous. Might be used as a target for male contraception. Lacks a cleavable signal sequence. Based on a readthrough transcript which may produce a EPPIN-WFDC6 fusion protein.

Isoforms (3)

UniProt ID	Names	Canonical?
O95925-1	1	yes
O95925-2	2, Eppin-2
O95925-3	3

RefSeq proteins (2): NP_001289790, NP_065131* (*=MANE)

Domains & families (InterPro)

ID	Name	Type
IPR002223	Kunitz_BPTI	Domain
IPR008197	WAP_dom	Domain
IPR020901	Prtase_inh_Kunz-CS	Conserved_site
IPR036645	Elafin-like_sf	Homologous_superfamily
IPR036880	Kunitz_BPTI_sf	Homologous_superfamily
IPR051388	Serpin_venom_toxin	Family

Pfam: PF00014, PF00095

UniProt features (24 total): disulfide bond 7, mutagenesis site 7, splice variant 2, sequence variant 2, domain 2, region of interest 2, signal peptide 1, chain 1

Structure

Experimental structures (PDB)

0 structures.

Predicted structure (AlphaFold)

Model	pLDDT	Fraction very-high
AF-O95925-F1	89.87	0.69

Functional residue map

Curated UniProt residues grouped by drug-discovery relevance — catalytic, ligand-binding, modification, and mutation-validated positions. Source: UniProtKB sequence features.

Disulfide bonds (7): 77–127, 86–110, 102–123, 33–61, 40–65, 48–60, 54–69

Mutagenesis-validated functional residues (7):

Position	Phenotype
87	loss of effect on klk3 activity.
102	reduces the binding to semg1 by 45%.
107	reduces the binding to semg1 by 68%.
110	does not affect the binding of semg1 or ltf. does not affect the binding of semg1; when associated with a-123 and a-127.
117	reduces the binding to semg1 by 68% and to ltf by 73%.
123	does not affect the binding of semg1 or ltf. does not affect the binding of semg1; when associated with a-110 and a-127.
127	does not affect the binding of semg1 or ltf. does not affect the binding of semg1; when associated with a-110 and a-123.

Function

Pathways and Gene Ontology

Reactome pathways

1 pathways

ID	Pathway
R-HSA-6803157	Antimicrobial peptides

MSigDB gene sets: 116 (showing top): GSE45365_HEALTHY_VS_MCMV_INFECTION_CD8_TCELL_IFNAR_KO_UP, GOBP_NEGATIVE_REGULATION_OF_REPRODUCTIVE_PROCESS, GOBP_NEGATIVE_REGULATION_OF_PROTEOLYSIS, REACTOME_INNATE_IMMUNE_SYSTEM, GOBP_REGULATION_OF_MICROTUBULE_BASED_PROCESS, GOCC_SECRETORY_GRANULE, GOBP_NEGATIVE_REGULATION_OF_HYDROLASE_ACTIVITY, GOCC_CELL_SURFACE, GOBP_MONOATOMIC_CATION_TRANSPORT, FERREIRA_EWINGS_SARCOMA_UNSTABLE_VS_STABLE_DN, GOBP_REGULATION_OF_HYDROLASE_ACTIVITY, GOBP_NEGATIVE_REGULATION_OF_TRANSPORT, GOBP_CALCIUM_ION_IMPORT, SENGUPTA_NASOPHARYNGEAL_CARCINOMA_DN, GOBP_NEGATIVE_REGULATION_OF_CALCIUM_ION_IMPORT

GO Biological Process (4): negative regulation of peptidase activity (GO:0010466), defense response to bacterium (GO:0042742), negative regulation of calcium ion import (GO:0090281), negative regulation of flagellated sperm motility (GO:1901318)

GO Molecular Function (3): serine-type endopeptidase inhibitor activity (GO:0004867), protein binding (GO:0005515), peptidase inhibitor activity (GO:0030414)

GO Cellular Component (7): acrosomal vesicle (GO:0001669), obsolete extracellular space (GO:0005615), cell surface (GO:0009986), protein-containing complex (GO:0032991), sperm plasma membrane (GO:0097524), extracellular region (GO:0005576), cytoplasm (GO:0005737)

Reactome top-level categories

Rollup of top-1 pathways:

Category	Pathways
Innate Immune System	1

GO top-level categories

Rollup of top GO terms by namespace:

Category	Terms
cellular anatomical structure	3
peptidase activity	2
negative regulation of proteolysis	1
negative regulation of hydrolase activity	1
regulation of peptidase activity	1
defense response	1
response to bacterium	1
negative regulation of calcium ion transport	1
calcium ion import	1
regulation of calcium ion import	1
negative regulation of cilium movement	1
flagellated sperm motility	1
regulation of flagellated sperm motility	1
negative regulation of cilium-dependent cell motility	1
negative regulation of reproductive process	1
serine-type endopeptidase activity	1
endopeptidase inhibitor activity	1
binding	1
enzyme inhibitor activity	1
peptidase regulator activity	1
secretory granule	1
cellular_component	1
plasma membrane	1
intracellular anatomical structure	1

Protein interactions and networks

STRING

864 interactions, top by confidence (×1000):

Protein A	Protein B	Partner UniProt	Score
EPPIN	SEMG1	P04279	755
EPPIN	SPINT4	Q6UDR6	717
EPPIN	ETV4	P43268	714
EPPIN	WFDC10A	Q9H1F0	611
EPPIN	GATA1	P15976	548
EPPIN	DEFB126	Q9BYW3	541
EPPIN	CT55	Q8WUE5	506
EPPIN	CPXCR1	Q8N123	479
EPPIN	KLK3	P07288	479
EPPIN	TULP2	O00295	478
EPPIN	WFDC3	Q8IUB2	437
EPPIN	WFDC9	Q8NEX5	435
EPPIN	CRISP2	P16562	434
EPPIN	JUN	P05412	411
EPPIN	SEMG2	Q02383	403

IntAct

4 interactions, top by confidence:

A	B	Type	Score
EPPIN	UMPS	psi-mi:“MI:0914”(association)	0.530
EPPIN	HSPA5	psi-mi:“MI:0914”(association)	0.350
EPPIN		psi-mi:“MI:0915”(physical association)	0.000

BioGRID (10): LTF (Co-fractionation), CLU (Co-fractionation), EPPIN (Affinity Capture-Western), LTF (Far Western), CLU (Far Western), UMPS (Affinity Capture-MS), HSPA5 (Affinity Capture-MS), UMPS (Affinity Capture-MS), ADAM9 (Affinity Capture-MS), EPPIN (Protein-RNA)

ESM2 similar proteins: A4K2P0, A5X2X1, A6MFL2, A7X3V4, A7X3V7, A7X4K1, A8Y7N4, A8Y7N7, A8Y7N8, A8Y7N9, A8Y7P5, B2BS84, B2KTG1, B5KF95, B5KF96, B5KL34, B5KL36, B5L5Q8, B7S4N9, D4A2Z2, E5AJX3, F6ULY1, H6VC05, I2G9B4, O35536, O43278, O43291, O95925, P00974, P00991, P00992, P01173, P01174, P04815, Q08E66, Q29100, Q2ES46, Q3UW55, Q4KUS1, Q6T6S5

Diamond homologs: A0A6P8HC43, A5X2X1, A6MFL4, A7X3V4, B2BS84, B2KTG1, B5G6G6, B5KF95, B5KF96, B5KL36, B5L5M7, B5L5R0, B6ZIW0, B7S4N9, C0HJU6, C0HLB2, C0HMC7, C1IC50, C1IC53, F6ULY1, F8J2F3, H2A0P0, O43291, O54819, O95925, P00974, P00976, P00978, P00993, P00994, P02760, P04365, P04366, P04815, P05067, P08592, P0C8W3, P0DN06, P0DN07, P0DN08

SIGNOR signaling

0 interactions.

Disease & clinical

Clinical variants and AI predictions

ClinVar

1 variants total. Per-class counts are floors (≥ shown; pagination cap):

Classification	Count (floor)
Pathogenic	0
Likely pathogenic	0
Uncertain significance	1
Likely benign	0
Benign	0

Top pathogenic / likely-pathogenic (0)

SpliceAI

491 predictions. Top by Δscore:

Variant	Effect	Δscore
20:45542769:C:CT	acceptor_gain	1.0000
20:45547263:TTA:T	donor_loss	1.0000
20:45547264:TAC:T	donor_loss	1.0000
20:45547265:A:AC	donor_gain	1.0000
20:45547265:ACTGG:A	donor_loss	1.0000
20:45547266:C:CG	donor_gain	1.0000
20:45547266:C:CT	donor_gain	1.0000
20:45547266:CT:C	donor_gain	1.0000
20:45547266:CTG:C	donor_gain	1.0000
20:45547266:CTGG:C	donor_gain	1.0000
20:45547266:CTGGG:C	donor_gain	1.0000
20:45547261:ACTT:A	donor_loss	0.9900
20:45547262:CTTA:C	donor_gain	0.9900
20:45541386:G:C	acceptor_gain	0.9800
20:45546402:T:TC	acceptor_gain	0.9800
20:45547296:C:A	donor_gain	0.9700
20:45545633:TATTA:T	donor_loss	0.9600
20:45545634:ATTAC:A	donor_loss	0.9600
20:45545635:TTACC:T	donor_loss	0.9600
20:45545636:TACCT:T	donor_loss	0.9600
20:45545637:ACC:A	donor_loss	0.9600
20:45545637:ACCTT:A	donor_loss	0.9600
20:45545638:C:A	donor_loss	0.9600
20:45545769:CC:C	acceptor_gain	0.9600
20:45545770:CC:C	acceptor_gain	0.9600
20:45547261:A:AC	donor_gain	0.9600
20:45547262:C:CC	donor_gain	0.9600
20:45542814:A:T	acceptor_gain	0.9500
20:45545687:T:TA	donor_gain	0.9500
20:45545767:CTCC:C	acceptor_gain	0.9500

AlphaMissense

889 scored. Top likely-pathogenic:

Variant	Protein change	am_pathogenicity
20:45542776:A:C	F105L	0.973
20:45542776:A:T	F105L	0.973
20:45542778:A:G	F105L	0.973
20:45542740:G:C	F117L	0.972
20:45542740:G:T	F117L	0.972
20:45542742:A:G	F117L	0.972
20:45542777:A:C	F105C	0.963
20:45542741:A:C	F117C	0.954
20:45545673:G:C	F63L	0.951
20:45545673:G:T	F63L	0.951
20:45545675:A:G	F63L	0.951
20:45545674:A:C	F63C	0.930
20:45542762:C:G	C110S	0.922
20:45542763:A:T	C110S	0.922
20:45542723:C:G	C123S	0.905
20:45542724:A:T	C123S	0.905
20:45542861:C:G	C77S	0.905
20:45542862:A:T	C77S	0.905
20:45545656:C:G	C69S	0.903
20:45545657:A:T	C69S	0.903
20:45545719:C:G	C48S	0.902
20:45545720:A:T	C48S	0.902
20:45542741:A:G	F117S	0.901
20:45545701:C:G	C54S	0.901
20:45545702:A:T	C54S	0.901
20:45542747:T:A	N115I	0.893
20:45542786:C:G	C102S	0.889
20:45542787:A:T	C102S	0.889
20:45542834:C:G	C86S	0.886
20:45542835:A:T	C86S	0.886

dbSNP variants (sampled 300 via entrez): RS1000113555 (20:45542069 C>T), RS1000310170 (20:45546404 G>T), RS1000312325 (20:45547619 G>A,T), RS1000429870 (20:45546738 A>G), RS1001416692 (20:45541372 A>G), RS1001947251 (20:45547171 T>A,C), RS1002336740 (20:45546077 G>C), RS1002953006 (20:45543679 T>G), RS1003013862 (20:45548699 T>C), RS1003310675 (20:45545089 GTAT>G), RS1003710659 (20:45542646 G>C), RS1003824274 (20:45546290 G>T), RS1004553631 (20:45544159 G>A), RS1004985522 (20:45545812 A>C,G), RS1005820510 (20:45545582 G>A)

Disease associations

OMIM: gene MIM:609031 | disease phenotypes:

GenCC curated gene-disease

Mondo (0):

Orphanet (0):

HPO phenotypes

0 total (0 of 0 shown, HPO-id order):

GWAS associations

0 associations (top):

Drugs & pharmacology

Drug and pharmacology data

Is drug target: no

PharmGKB: 1 entry (VIP=true, CPIC=false)

CTD chemical–gene interactions

11 total (human), top 11 by PubMed support.

Chemical	Actions (top 5)	PubMed papers
CGP 52608	increases reaction, affects binding	1
Resveratrol	affects cotreatment, decreases expression	1
Air Pollutants	increases abundance, increases expression	1
Benzo(a)pyrene	affects methylation, decreases methylation, increases methylation	1
Dimethyl Sulfoxide	affects expression	1
Plant Extracts	affects cotreatment, decreases expression	1
Smoke	increases abundance, increases expression	1
Tobacco Smoke Pollution	decreases expression	1
Valproic Acid	decreases methylation	1
Aflatoxin B1	increases methylation	1
Cadmium Chloride	decreases expression	1

Clinical trials (associated diseases)

0 trials via MONDO — disease-level, not drug-specific.