ATRX silences Cartpt expression in osteoblastic cells during skeletal development.

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• ATRX is crucial for DNA maintenance, chromatin regulation, and gene expression during development.
• X-linked α-thalassemia mental retardation (ATR-X) syndrome is caused by ATRX mutations, leading to developmental and skeletal abnormalities.
• Previous studies explored ATRX's role in skeletal development via tissue-specific knockouts, but early development impacts remain unclear.

Purpose of the Study:

• To investigate the role of ATRX in early skeletal development.
• To elucidate the molecular mechanisms by which ATRX influences bone formation and remodeling.

Main Methods:

• Utilized preosteoblast-specific Atrx conditional knockout mice.
• Performed in vitro co-culture of Atrx conditional knockout bone marrow stromal cells (BMSCs) with wild-type (WT) splenocytes.
• Analyzed gene expression, including receptor activator of nuclear factor κ-B ligand (Rankl) and osteoprotegerin (Opg).
• Investigated the role of cocaine- and amphetamine-regulated transcript (Cartpt) and its regulation by ATRX.

Main Results:

• Atrx deletion in preosteoblasts resulted in increased trabecular bone mass and reduced osteoclast numbers.
• Impaired osteoclast differentiation was observed in vitro.
• Atrx deficiency led to a decreased Rankl/Opg expression ratio in BMSCs.
• ATRX-deficient cells showed elevated Cartpt expression, which was suppressed by ATRX binding to the promoter.

Conclusions:

• ATRX acts as a potent repressor of Cartpt expression during skeletal development.
• ATRX deficiency disrupts the delicate balance of bone remodeling by altering osteoclastogenesis via Cartpt regulation.
• Targeting Cartpt may offer therapeutic potential for skeletal disorders associated with ATRX dysfunction.