Life and health

Existential therapy

Existential therapy, also known as existential psychotherapy, is a talk therapy rooted in European existential philosophy and developed after World War II by Viktor Frankl, Rollo May, and Irvin Yalom.

Exisulind

Exisulind (sulindac sulfone, Aptosyn, FGN-1) is the non-COX-inhibitory sulfone metabolite of sulindac; a cGMP PDE inhibitor that induces apoptosis, it reached phase 3 for colonic polyps but failed FDA approval in 2000 over hepatotoxicity.

Exo-beta-D-glucosaminidase

Exo-β-D-glucosaminidase (EC 3.2.1.165; GlcNase, exochitosanase, GlmA, CsxA) is an exo-hydrolase removing D-glucosamine from the non-reducing ends of chitosan oligosaccharides; archaeal GlmA is a thermostable GH35 homodimer, bacterial versions are GH2.

EXO1

EXO1 (exonuclease 1, HEX1, MIM:606063) is a human gene at 1q43 encoding a 5'-3' exonuclease used in mismatch repair, double-strand break resection, and telomere maintenance; its proposed Lynch syndrome link was refuted by ClinGen in 2023.

Exobasidiomycetes

Exobasidiomycetes (Exobasidiomycetidae) is a class of smut fungi and allies in Ustilaginomycotina, Basidiomycota, with seven orders including Exobasidiales and Tilletiales; the class is paraphyletic.

EXOC6B-related spondyloepimetaphyseal dysplasia with joint laxity

EXOC6B-related spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL3, OMIM 618395) is an ultra-rare autosomal recessive skeletal dysplasia from biallelic EXOC6B variants, causing congenital hip and knee dislocations, joint laxity, short stature, and impaired ciliogenesis.

Exocrine cell

Exocrine cell: an epithelial cell secreting via ducts onto body surfaces (salivary, sweat, sebaceous, lacrimal, mammary, pancreatic acinar cells), unlike endocrine cells that secrete into blood; serous, mucous, and lipid cell types.

Exocrine gland

An exocrine gland, known in Latin as glandula exocrina, releases substances such as sweat, tears, saliva, milk, and digestive juices through a duct onto a body surface.

Exocrine pancreatic insufficiency

Exocrine pancreatic insufficiency (EPI, PEI) is inadequate delivery of pancreatic digestive enzymes to the intestine, causing maldigestion. Main causes: chronic pancreatitis, cystic fibrosis, pancreatic cancer, surgery. Diagnosed by fecal elastase (<200 µg/g), treated with pancreatic enzyme replacement therapy.

Exocyst complex component Exo70

Exo70 (EXO70, Exocyst complex component 7) is the ~70 kDa plasma-membrane-targeting subunit of the octameric exocyst vesicle-tethering complex; it binds PI(4,5)P2 and Arp2/3, and in land plants expanded into 13-47 paralogs in three subfamilies.

Exocyst complex component EXOC2/Sec5, N-terminal domain

N-terminal domain of EXOC2/Sec5, the exocyst complex component 2: an IPT/TIG immunoglobulin-like fold (human residues 8-91) that binds activated Ral GTPases, carries the CorEx assembly motif pairing with Sec3, and when truncated causes autosomal recessive neurodevelopmental disorder.

Exocyst complex component EXOC6/Sec15

EXOC6, or Sec15, is the human exocyst complex component 6, one of eight subunits of the octameric vesicle-tethering exocyst. Its C-terminus binds Rab GTPases (Sec4 in yeast, Rab11 in mammals); EXOC6B mutations cause SEMDJL3.

Exocytosis

Exocytosis: vesicle-plasma membrane fusion releasing cell contents. Two pathways, constitutive (all cells) and regulated (neurons, endocrine, exocrine cells, Ca2+-triggered via SNAREs, synaptotagmin); modes include full-collapse, kiss-and-run, compound fusion.

Exodeoxyribonuclease 8

Exodeoxyribonuclease 8 (Exonuclease VIII, RecE, UniProt P15032) is an E. coli Rac prophage ATP-independent Mg2+-dependent 5' to 3' dsDNA exonuclease, functional equivalent of lambda exonuclease, partner of RecT in RecET recombineering.

Exogyra

Exogyra (Say, 1820) is an extinct Cretaceous gryphaeid oyster genus, type species E. costata, ranging Berriasian to Maastrichtian across North America, Europe, Africa, and Asia, abundant in Gulf Coastal Plain strata.

Exome

The exome is the sequence of all exons in a genome, the roughly 1-2 percent of human DNA that codes for proteins across about 20,000 genes; whole exome sequencing targets it for lower-cost disease-variant discovery than whole genome sequencing.

Exome sequencing

Exome sequencing (whole exome sequencing, WES) determines the DNA sequence of all exons, about 1–2% of the genome. Using targeted capture plus next-generation sequencing, it yields 25–57% diagnoses in rare disease but misses non-coding, structural, and repeat variants.

Exomer complex component Chs5

Chs5 (Chs5p, CHS5, Q12114) is the fungal core scaffold of the exomer cargo adaptor, a Chs5 homodimer bound to two ChAPs (Chs6, Bud7, Bch1, Bch2) that sorts Chs3 and other cargo from the TGN to the plasma membrane via Arf1.

Exon

Exon: gene regions retained in mature RNA after introns are spliced out; term coined by Walter Gilbert in 1978. Exons are about 1% of the human genome, may be coding or untranslated, and recombine by exon shuffling.

Exon junction complex

Exon junction complex (EJC): a four-protein complex (eIF4A3, Y14/RBM8A, MAGOH, MLN51/CASC3) deposited by the spliceosome 20–24 nt upstream of exon–exon junctions during splicing, regulating mRNA export, translation, localization, and nonsense-mediated decay until removed during the first translation round.

Exon skipping

Exon skipping: antisense oligonucleotide therapy for Duchenne muscular dystrophy that masks a dystrophin pre-mRNA exon to restore the reading frame; FDA-approved drugs include eteplirsen (exon 51), golodirsen and viltolarsen (exon 53), and casimersen (exon 45).

Exonuclease

Exonuclease: enzyme that cleaves nucleotides from the ends of DNA or RNA chains. 3'→5' exonucleases proofread DNA replication (pol I, III, δ, ε); 5'→3' exonucleases remove RNA primers; includes autonomous TREX1/2 and lambda exonuclease.

Exonuclease V

Exonuclease V (EC 3.1.11.5), also called RecBCD, is the ATP-dependent double-strand DNA exonuclease of E. coli, a helicase-nuclease complex regulated by Chi sites that repairs double-strand breaks; AddAB and AdnAB are its functional analogues.

Exophiala

Exophiala, black yeast genus (Chaetothyriales) of melanized fungi from warm, humid habitats; species such as E. dermatitidis cause skin disease, cystic fibrosis colonization, and rare fungemia with about 34% mortality.

Exophthalmos

Exophthalmos, also called proptosis, is the bulging of one or both eyes from the orbit, the bony socket. In adults it is most often caused by Graves disease.

Exopolyphosphatase

Exopolyphosphatase (PPX, EC 3.6.1.11), also called metaphosphatase, processively hydrolyzes terminal phosphates from inorganic polyphosphate to release orthophosphate; key bacterial polyP-degrading enzyme, Mg2+/K+-dependent, inhibited by pppGpp.

EXOSC10

EXOSC10 (Rrp6, PM/Scl-100), human nuclear-specific distributive 3'→5' exoribonuclease of the RNA exosome; matures 5.8S rRNA and snoRNAs in the nucleolus, clears dilncRNAs at DNA breaks, and is a 5-FU sensitivity gene.

Exoskeleton

Exoskeleton: the rigid external skeleton of arthropods, made of chitin in a protein matrix, often calcified in crustaceans; it supports and protects the body but must be shed by molting for growth.

Exoskeleton Device

Exoskeleton Device (MeSH, robotic exoskeleton): wearable external devices supporting the musculoskeletal system for gait, lifting, and rehabilitation; passive and active types with quantified occupational and clinical evidence.