OSMRβ mutants enhance basal keratinocyte differentiation via inactivation of the STAT5/KLF7 axis in PLCA patients

Krüppel-like factor 7 deficiency disrupts corpus callosum development and neuronal migration in the developing mouse cerebral cortex

Krüppel-like Factor 7 (KLF7) is a zinc finger transcription factor that has a critical role in cellular differentiation, tumorigenesis, and regeneration. Mutations in Klf7 are associated with autism spectrum disorder, which is characterized by neurodevelopmental delay and intellectual disability. Here we show that KLF7 regulates neurogenesis and neuronal migration during mouse cortical development. Conditional depletion of KLF7 in neural progenitor cells resulted in agenesis of the corpus callosum, defects in neurogenesis, and impaired neuronal migration in the neocortex. Transcriptomic profiling analysis indicated that KLF7 regulates a cohort of genes involved in neuronal differentiation and migration, including p21 and Rac3. These findings provide insights into our understanding of the potential mechanisms underlying neurological defects associated with Klf7 mutations.

AHNAK, regulated by the OSM/OSMR signaling, involved in the development of primary localized cutaneous amyloidosis

BACKGROUND

Primary localized cutaneous amyloidosis (PLCA) is a chronic skin disease characterized by aberrant keratinocyte differentiation, epidermal hyperproliferation, and amyloid deposits. Previously, we demonstrated OSMR loss-function mutants enhanced basal keratinocyte differentiation through the OSMR/STAT5/KLF7 signaling in PLCA patients.

OBJECTIVE

To investigate the underlying mechanisms involved in basal keratinocyte proliferation in PLCA patients that remain unclear.

METHODS

Patients with pathologically confirmed PLCA visiting the dermatologic outpatient clinic were involved in the study. Laser capture microdissection and mass spectrometry analysis, gene-edited mice, 3D human epidermis culture, flow cytometry, western blot, qRT-PCR and RNA sequencing were used to explore the underlying molecular mechanisms.

RESULTS

In this study, we found that AHNAK peptide fragments were enriched in the lesions of PLCA patients, as detected by laser capture microdissection and mass spectrometry analysis. The upregulated expression of AHNAK was further confirmed using immunohistochemical staining. qRT-PCR and flow cytometry revealed that pre-treatment with OSM can inhibit AHNAK expression in HaCaT cells, NHEKs, and 3D human skin models, but OSMR knockout or OSMR mutations abolished this down-regulation trend. Similar results were obtained in wild-type and OSMR knockout mice. More importantly, EdU incorporation and FACS assays demonstrated the knockdown of AHNAK could induce G1 phase cell cycle arrest and inhibit keratinocyte proliferation. Furthermore, RNA sequencing revealed that AHNAK knockdown regulated keratinocyte differentiation.

CONCLUSION

Taken together, these data indicated that the elevated expression of AHNAK by OSMR mutations led to hyperproliferation and overdifferentiation of keratinocytes, and the discovered mechanism might provide insights into potential therapeutic targets for PLCA.

Generation of a human embryonic stem cell line (SMUDHe010-A-82) carrying a homozygous c.1538G > A (p.G513D) mutation in the OSMR gene by CRISPR/Cas9-mediated homologous recombination

Mutations in the tumor suppressor M receptor (OSMR) gene are associated with primary localized cutaneous amyloidosis (PLCA). Recently, we confirmed that OSMR loss-of-function mutations enhance epidermal keratinocyte differentiation via inactivation of the STAT5/KLF7 signaling. However, no disease model was available for PLCA. Accordingly, we generated an OSMR c.1538G > A mutant human embryonic stem cell line (SMUDHe010-A-82) using CRISPR/Cas9-mediated homologous recombination. The cell line preserves normal karyotype, pluripotency and the ability to differentiate into all three germ layers. Moreover, the cell line can be used to prepare human skin organoid, which may provide a disease model for PLCA.

Oncostatin M sensitizes keratinocytes to UVB-induced inflammation via GSDME-mediated pyroptosis

BACKGROUND

Oncostatin M (OSM), an interleukin-6 (IL-6) family proinflammatory cytokine, plays a critical role in inflammatory skin diseases, but its mechanism of action is not well understood.

OBJECTIVE

To demonstrate the mechanism of OSM induced pyropotosis in normal human epidermal keratinocytes (NHEKs) and immortalized human keratinocytes (HaCaT cells).

METHODS

NHEKs and HaCaT cells were treated with OSM. Knockout of OSM receptor (OSMR) with CRISPR/Cas9 system, knockdown of GSDME with small interfering RNA and primary keratinocytes from Osmr-/- and Gsdme-/- mice were used to study the effect of OSMR and GSDME. After treatment of OSM, NHEKs and HaCaT cells were irradiated with UVB. The mRNA was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) and RNA sequencing, protein level was detected by Western Blotting, Elisa and immunofluorescence. Cell death was examined by lactate dehydrogenase (LDH) releasing.

RESULTS

Here we found that OSM induced pyropotosis in NHEKs and HaCaT cells, but knockout of OSMR abolished pyropotosis. RNA sequencing revealed an upregulation of several key genes involved in NLRP3 inflammasome activation following OSM treatment, among which NLRP3, GSDME, and IL-1β were confirmed by qRT-PCR and Western Blotting. Knockdown of GSDME alleviated OSM-induced pyropotosis. Pretreatment of OSM boosted UVB-induced pyroptosis and inflammation in NHEKs and HaCaT cells, and this priming function was lost in keratinocytes of Osmr-/- and Gsdme-/- mice. Similar results were obtained in a 3-dimensional culture of human epidermis.

CONCLUSION

OSM functions as a priming cytokine to enhance UVB-induced inflammation in keratinocytes, providing insight into the pathogenesis of inflammatory skin diseases.