diff --git a/src/ontology/cl-edit.owl b/src/ontology/cl-edit.owl
index 7ba6fdb8f..0ef42f204 100644
--- a/src/ontology/cl-edit.owl
+++ b/src/ontology/cl-edit.owl
@@ -3125,6 +3125,7 @@ Declaration(Class(obo:CL_4052022))
 Declaration(Class(obo:CL_4052023))
 Declaration(Class(obo:CL_4052024))
 Declaration(Class(obo:CL_4052025))
+Declaration(Class(obo:CL_4052026))
 Declaration(Class(obo:CL_4052027))
 Declaration(Class(obo:CL_4052048))
 Declaration(Class(obo:CL_4052049))
@@ -33150,6 +33151,20 @@ AnnotationAssertion(Annotation(oboInOwl:hasSynonymType obo:OMO_0003000) oboInOwl
 AnnotationAssertion(rdfs:label obo:CL_4052025 "neuromuscular junction nucleus")
 EquivalentClasses(obo:CL_4052025 ObjectIntersectionOf(obo:GO_0005634 ObjectSomeValuesFrom(obo:BFO_0000050 obo:CL_0008046) ObjectSomeValuesFrom(obo:RO_0002131 obo:GO_0098522)))
 
+# Class: obo:CL_4052026 (type IIx muscle cell)
+
+AnnotationAssertion(Annotation(oboInOwl:hasDbXref "PMID:34727990") Annotation(oboInOwl:hasDbXref "PMID:35908794") Annotation(oboInOwl:hasDbXref "PMID:36361732") Annotation(oboInOwl:hasDbXref "doi:10.1101/2024.05.15.594276") obo:IAO_0000115 obo:CL_4052026 "A fast type II muscle cell that is part of the skeletal muscle tissue. This cell is characterized by its intermediate metabolic profile, utilizing both glycolytic and oxidative pathways for energy production. In humans, it is distinguished by the expression of myosin heavy chain 1 (MYH1).")
+AnnotationAssertion(terms:contributor obo:CL_4052026 <https://orcid.org/0009-0000-8480-9277>)
+AnnotationAssertion(terms:date obo:CL_4052026 "2024-11-04T10:26:29Z"^^xsd:dateTime)
+AnnotationAssertion(Annotation(oboInOwl:hasDbXref "PMID:34727990") oboInOwl:hasExactSynonym obo:CL_4052026 "type 2x muscle cell")
+AnnotationAssertion(Annotation(oboInOwl:hasDbXref "PMID:34727990") oboInOwl:hasExactSynonym obo:CL_4052026 "type 2x muscle fiber")
+AnnotationAssertion(Annotation(oboInOwl:hasDbXref "doi:10.1101/2024.05.15.594276") oboInOwl:hasExactSynonym obo:CL_4052026 "type IIx muscle fiber")
+AnnotationAssertion(Annotation(oboInOwl:hasDbXref "PMID:34727990") oboInOwl:hasExactSynonym obo:CL_4052026 "type 2x fiber")
+AnnotationAssertion(Annotation(oboInOwl:hasDbXref "PMID:34727990") Annotation(oboInOwl:hasDbXref "PMID:27199166") rdfs:comment obo:CL_4052026 "In humans, type IIx fiber contains high levels of MYLK2, enhancing contraction speed and force via myosin phosphorylation, especially under low calcium. This mechanism supports post-activation potentiation, increasing force output in fast-twitch muscles. Additionally, this fiber has abundant ACTN3 (α-actinin-3), linked to muscle power, and exhibits the highest shortening velocity among human muscle fiber types. Notably, type IIx fiber is selectively lost in aging-related sarcopenia, increases in proportion in type 2 diabetes and obesity, and is the first to degenerate in Duchenne Muscular Dystrophy, impacting muscle function across various conditions.")
+AnnotationAssertion(rdfs:label obo:CL_4052026 "type IIx muscle cell")
+SubClassOf(obo:CL_4052026 obo:CL_0002212)
+SubClassOf(obo:CL_4052026 ObjectSomeValuesFrom(obo:BFO_0000050 obo:UBERON_0001134))
+
 # Class: obo:CL_4052027 (atretic theca cell)
 
 AnnotationAssertion(Annotation(oboInOwl:hasDbXref "PMID:20628033") Annotation(oboInOwl:hasDbXref "PMID:38069168") obo:IAO_0000115 obo:CL_4052027 "A theca cell undergoing atresia, characterized by distinct morphological changes including hypertrophy, altered cell shape, and disrupted layered organization. This cell exhibits reduced steroidogenic capacity and changes in surrounding vascularization. The onset of theca cell atresia can vary, occurring at different stages of follicle atresia depending on the phase of folliculogenesis.")