Identification of limb-specific Lmx1b auto-regulatory modules with Nail-patella syndrome pathogenicity.
Nat Commun 2021;
12:5533. [PMID:
34545091 PMCID:
PMC8452625 DOI:
10.1038/s41467-021-25844-5]
[Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 08/31/2021] [Indexed: 01/18/2023] Open
Abstract
LMX1B haploinsufficiency causes Nail-patella syndrome (NPS; MIM 161200), characterized by nail dysplasia, absent/hypoplastic patellae, chronic kidney disease, and glaucoma. Accordingly in mice, Lmx1b has been shown to play crucial roles in the development of the limb, kidney and eye. Although one functional allele of Lmx1b appears adequate for development, Lmx1b null mice display ventral-ventral distal limbs with abnormal kidney, eye and cerebellar development, more disruptive, but fully concordant with NPS. In Lmx1b functional knockouts (KOs), Lmx1b transcription in the limb is decreased nearly 6-fold, indicating autoregulation. Herein, we report on two conserved Lmx1b-associated cis-regulatory modules (LARM1 and LARM2) that are bound by Lmx1b, amplify Lmx1b expression with unique spatial modularity in the limb, and are necessary for Lmx1b-mediated limb dorsalization. These enhancers, being conserved across vertebrates (including coelacanth, but not other fish species), and required for normal locomotion, provide a unique opportunity to study the role of dorsalization in the fin to limb transition. We also report on two NPS patient families with normal LMX1B coding sequence, but with loss-of-function variations in the LARM1/2 region, stressing the role of regulatory modules in disease pathogenesis.
Nail-patella syndrome (NPS) is characterized by nail dysplasia, absent/hypoplastic patellae, chronic kidney disease, and glaucoma and can be caused by haploinsufficiency of LMX1B; however, not all patients harbor pathogenic LMX1B mutations. Here the authors show that loss-of-function variations in upstream enhancer sequences are responsible for a limb specific form of human NPS.
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