This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "axial_segmentation_serial_homology#Vertebral and Costal Malsegmentation"). The biological motivation is serial homology: vertebrae and ribs are serially repeated somite derivatives built by one periodic segmentation mechanism, so a single clock/Notch lesion yields a multi-segment axial malformation bundle rather than an isolated defect. Conforming nodes should substitute the disorder-specific lesion at the trigger node (DLL3/SCDO1, MESP2/SCDO2, LFNG/SCDO3, HES7/SCDO4, TBX6) and specialize the affected vertebral/costal elements at the consequence node. Modules bind GO and CL terms only.
Segmentation Clock and Wavefront Dysfunction
trigger
The conserved initiating lesion disrupts the segmentation clock — the oscillatory network of coupled Notch, Wnt, and FGF signaling in the presomitic mesoderm — or the FGF/Wnt determination wavefront that converts the clock's temporal periodicity into spatial segment boundaries. In humans, the recurrent lesions are in Notch-pathway components (DLL3, MESP2, LFNG, HES7) and the mesoderm regulator TBX6; proper regulation of Notch signaling is an absolute requirement for correct patterning of the axial skeleton.
Downstream
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Disrupted Somite Boundary Formation
Show evidence (3 references)
"These genes are important components of the Notch signaling pathway, which has multiple roles in development and disease."
Identifies the human spondylocostal dysostosis genes (DLL3, MESP2, LFNG) as Notch-pathway components, the conserved trigger of this module. Evidence source is HUMAN_CLINICAL because the genes were identified in affected families.
"proper regulation of the Notch signaling pathway is an absolute requirement for the correct patterning of the axial skeleton."
States that intact Notch signaling is required for axial-skeleton patterning, linking the trigger lesion to the module's downstream outcome. Evidence source is HUMAN_CLINICAL because it is drawn from human mutation-phenotype analysis.
"conditional deletion of the FGF receptor gene Fgfr1 abolishes FGF signaling in the mouse PSM, resulting in an arrest of the dynamic cyclic gene expression and ultimately leading to an arrest of segmentation."
Shows that disrupting FGF signaling halts the cyclic segmentation-clock gene expression and arrests segmentation. Evidence source is MODEL_ORGANISM because this is a mouse conditional-knockout study.
Vertebral and Costal Malsegmentation
consequence
Because the vertebrae and ribs are serially homologous somite derivatives built by one periodic mechanism, mis-segmentation produces a coordinated multi-segment malformation bundle rather than an isolated defect: multiple hemivertebrae, fused/block vertebrae, and rib fusions or malalignment along the axial skeleton, frequently causing congenital scoliosis and thoracic insufficiency.
Show evidence (2 references)
"The spondylocostal dysostoses (SCDs) are a heterogeneous group of vertebral malsegmentation disorders that arise during embryonic development by a disruption of somitogenesis."
Defines the consequence — vertebral malsegmentation arising from disrupted somitogenesis. Evidence source is OTHER because this is a definitional review statement of the disease class.
"Patients with spondylocostal dysostosis (SCD) have congenital spine and rib deformities associated with frequently severe thoracic insufficiency and respiratory compromise."
Documents the serially homologous axial bundle — combined congenital spine and rib deformities with thoracic insufficiency — in human patients. Evidence source is HUMAN_CLINICAL.