Endometriosis, a complex gynecological disease, significantly impacts the reproductive health of women. Our study aimed to unravel the molecular mechanisms underlying the progression of endometriosis, utilizing comprehensive analysis of gene expression datasets through various bioinformatics tools.
The examination of gene expression profiles led to the identification of 552 differentially expressed genes (DEGs), including 312 up-regulated and 240 down-regulated genes. The up-regulated DEGs were found to be associated with essential biological processes such as cytokine-mediated signaling pathway, cellular response to stress, hormone-mediated signaling, lipid transport, and response to endogenous stimuli. Molecular functions of these up-regulated DEGs included lipase, kinase, lipoprotein, enzyme and cytoskeleton protein binding, enzyme activator, and phospholipase activity. They were also integral components of cellular structures such as the cytoskeleton, cytoplasmic vesicle, cell junctions, endomembrane system, Golgi apparatus, and plasma membrane.
Conversely, down-regulated DEGs were implicated in biological processes like proteolysis, gland and immune system development, integrin-mediated signaling, intracellular signaling, and protein kinase cascade. Their molecular functions involved signal peptidase, apical junction, cell-cell junction complex, perinuclear regions, and plasma membrane, with cellular components related to lysosphingolipid, lysophosphatidic acid, and identical protein binding.
Key hub nodes in the protein-protein interaction network were identified, with up-regulated DEGs including C3, APP, GNG12, PSAP, and GNAQ, while LPAR1, RAB3D, PIK3R1, TRIM32, and CMTM6 represented down-regulated DEGs. These hub nodes play crucial roles in the intricate molecular landscape of endometriosis.
C3 (Complement Component 3) is one of the important complement proteins out of 30 recognized till date. C3 has intensive and pivotal role in complement activation in both classical and alternative pathways. The alternative pathway is independent of antigen-antibody complexes and can directly be induced by components of cell wall of bacteria or present on the surface of damaged host cell via C3 unlike classical and lectin pathway [19]. Altered immune system is among the various risk factors which are involved in pathophysiology of endometriosis and hence deregulated C3 (which is an important player of immune system) might be involved in the progression of endometriosis and can be considered as a potent biomarker.
APP (Amyloid precursor protein), plays an important role in synaptic activity and neuronal plasticity, but upto this time it’s not completely revealed [20]. APP gene has been found to be associated with down’s syndrome [21]. Mutation in APP gene were also found to be associated with dementia and Alzimers disease including amyloid deposition, neurofibrillary tangle formation and cerebral amyloid angiopathy (CAA)[22]. APP is involved in the proliferation, migration and adhesion of endothelial cells. It mediates stability to focal adhesion and cell-cell junctions, while it's necessary for VEGF-A growth factor responses [23].Thus, it can be said that APP may be a factor to be involved in the adhesion and cellular junction formation of endometrial tissues during endometriosis.
GNG12 is known as the c12 subunit of G protein, and G proteins are made by three different subunits a, b and c making heterotrimeric. The different subunits are interchangeable, making possible combinations and wide array of effects. GNG12 is highly conserved, as and its homologs are present in human, rat, cow, frog, chicken and zebrafish. C12 is expressed differentially in mammalian brain, where its localized in glial cells and expressed in reactive astrocytes [24].
PSAP (Prosaposin, also known as SGP-1) is an intriguing multifunctional protein that plays roles intracellularly in regulation of lysosomal enzyme functions, and extracellularly, as a secretary factor having both neuroprotective and glioprotective effects. PSAP gene encodes a 524 amino-acid precursor protein prosaposin (pSAP), that gives 4 small glycoproteins-saposins (SapA, B, C and D) [25]. Saposins, a sphingolipid activator protein that’s required for the function of lysosomal hydrolases. Mutation in PSAP gene (two null alleles) in an individual have pSap deficiency and suffer with fatal infantile lysosomal storage disease[26]. Defects of Sap A and SapC leads to atypical Krabbe and Gaucher disease [27]. Any defect in SapB results in MLD (metachromatic leukodystrophy) due to impaired degradation and accumulation of cerebroside-3 sulfate (sulfatide) [28], while SapD deficiency causes Farber disease in mice [29].
GNAQ (Gnaq) is a member of guanine nucleotide binding protein (G protein) subunits and is found abundantly in brain. Gnaq gene knocking shows serious nervous dysfunction and endocrine system in mice [30] .Gnaq gene mutation has been reported mostly in uveal melanoma [31]. Gnaq, Gq protein a-subunit, encoded by GNAQ gene, is a member of Gq/11subfamily of heterotrimeric G proteins and its ubiquitously expressed in mammalian cells [30,32]. GNAQ has role in cardiovascular system [31]s, cancer and autoimmune diseases [33]. It is found to be coupled with GPCRs in viral infections[34], but no any expression or mutation studies has been yet reported in endometriosis, adenomyosis or ovarian carcinoma.
PIK3R1
PI3K enzymes are lipid kinases, having a conserved sequences and phosphorylating the
inositol 30-OH groups of membrane phosphoinositides (PI).
Class I PI3K convert phosphoinositol bisphosphate (PIP2) [4,5] into phosphoinositol trisphosphate (PIP3) [3,4,5] a second messenger [35]. Class IA PI3K is composed of a heterodimer having a p110 catalytic subunit and a p85 regulatory subunit. Out of four PI3K catalytic subunit isoforms (PI3Ka, PI3Kb, PI3Kg, and PI3Kd), only PI3Ka and PI3Kb are ubiquitously expressed in the body and are frequently altered in cancer disease [36]. Three different genes PIK3R1, PIK3R2, and PIK3R3, encode p85-type subunits; p85a, p85b and p55g, respectively. The two of PIK3R1 and PIK3R2 are widely expressed in the body, whereas the third one PIK3R3 is expressed only in testis and brain of adults [37]. PIK3R1/p85a is isoform found abundantly, but in cancer patients its expression is reduced [38]. It’s a Tumor-Suppressor Gene and the most striking difference between p85a and p85b is that PIK3R1/p85a acts as a tumor suppressor while, PIK3R2/p85b is a cancer driver. The recent finding say that p85a subunit restrains the catalytic activity of PI3K [39] encourage testing the consequences of reducing p85a levels. Other study tells deletion of Pik3r1 led to a gradual change in hepatocyte morphology (liver) and with over time, mice develops hepatocellular carcinoma [40]s. These two observations confirm the deletion of Pik3r1 gene is a cause of tumor development, as similarly observed for tumor suppressors. Pik3r1 loss in mouse accelerates HER2/neu-induced mammary cancer development, in cultured human epithelial cells PIK3R1 knockdown cause transformational changes, while hemi-zygous deletion is a frequent event in breast cancer samples [41]. Mutation in PIK3R1 has been reported in breast, pancreatic, colon cancers [42] and in 8.5% cases of ovarian carcinoma [43] The PIK3 pathway is downstream regulated from RTK (receptor tyrosine kinase), that’s active in cancer lineages, including endometrial cancer (EC) [44]. PIK3 mutation has been reported in ovarian carcinoma but not in cases where patients suffer with endometriosis only[45] . While PI3K pathway has been found to be strongly implicated during the development of endometriosis [46].
LPAR1
Lysophosphatidic Acid, is a small phospholipid present in many mammalian cells and tissues [47]. It is involved in cell migration, survival, proliferation, cellular interactions and cytoskeleton changes [48]. A study on mare, suffering with endometriosis has indicated that concentration of LPA, its receptors, PGE2/PGF2 ration and CTGF secretion is altered during endometriosis [49]. LPA induces IL-8 (Interleukin-8) expression via LPA-1 receptor, Gi protein, MAPK/p38 and NF-kB signalling pathway. Where IL-8 protein stimulates endometrial cell migration, permeability, capillary tube formation and proliferation leading to angiogenesis during pregnancy [50]. Overexpression of all LPARs and enzymes occur responsible for LPA synthesis, during endometrial cancers, showing a positive correlation with myoinvasion and FIGO (International Federation of Gynecology and Obstetrics) stage [51]s. Recent study has demonstrated that LPA, acts as a mitogen and pro-invasive stimulus for endometrial and endometriotic cells acts via LPAR1 and LPAR3 (Lysophosphatidic Acid Receptors). It has demonstrated that LPA-dependent stimulus causes secretion of cathepsin B, a protease, which acts as a factor for endometriotic invasion [52].
RAB3D, is a GTPase of Rab family, plays a role as a central regulator of vesicular transport [53].A study reveals that the Rab3D is implicated in the subcellular localization and maturation of Immature Secretory granules (ISGs) [54]. Rabs are involved in membrane trafficking, cellular signalling, growth and development. Rabs and their effectors has been found to be overexpressed or undergone for loss of function in many disease including cancers and causes the disease progression[55] .Endometriosis is also an inflammatory disease and similarly Rab can play its role in endometriosis disease progression and adhesion.
GPR39, are G-protein coupled receptors present in the plasma membrane, which is distinct target for binding of extracellular Zn+ ions [56–58]. G-protein coupled receptors are a large family of seven-transmembrane proteins, which are all involved in a diverse array of extracellular stimuli [59]. Zinc is an important component of enzymes and proteins. It is also required for intracellular message transmission, protein synthesis, cell membrane maintenance and transport, regulation of neuronal, endocrinal system [60]s. In brain GPR39 zinc sensing receptor has a significant role in Alzheimer and Epilepsy [61]. Further investigations showed that GPR39 contributes its part in skin wound healing, thus having a positive role in the area of dermatology and stem cell therapy [62]. A study has revealed that GPR39 might be a direct promising target for therapy of zincergic dyshomeostasis observed in Alzheimer’s disease, but more studies are still needed over it [63].
HOXC4, is actively transcribed during the development and differentiation of Lymphoid, myeloid and erythroid cells. It helps to maintain proliferation in hematopoietic cells[64].
Cystatin A (CSTA), is a type 1 cystatin super-family member, and is expressed mainly in epithelial and lymphoid tissues. It prevents the proteolysis of cytoplasmic and cytoskeletal proteins in cells. It acts a tumor suppressor in esophageal and lung cancer [65]. The risk of disease recurrence and death are found to be higher in patients suffering with squamous cell carcinoma of head and neck, having low CSTA[66] .Here expression analysis of DEGs in endometriosis, CSTA was found to be downregulated but detailed studies for the role of CSTA in endometriosis disease progression is still has to be done.
Epithelial splicing regulatory protein 1 (ESRP1), plays crucial role during organogenesis of craniofacial and epidermal development, branching morphogenesis in the lungs and salivary glands. It also plays role during cancer progression, and its expression found to be low in normal epithelium but upregulated during carcinoma [67]s.