Asxl1 exerts an antiproliferative effect on mouse lung maturation via epigenetic repression of the E2f1-Nmyc axis

Additional Sex Combs-like Family Associated with Epigenetic Regulation

The additional sex combs-like (ASXL) family, a mammalian homolog of the additional sex combs (Asx) of Drosophila, has been implicated in transcriptional regulation via chromatin modifications. Abnormal expression of ASXL family genes leads to myelodysplastic syndromes and various types of leukemia. De novo mutation of these genes also causes developmental disorders. Genes in this family and their neighbor genes are evolutionary conserved in humans and mice. This review provides a comprehensive summary of epigenetic regulations associated with ASXL family genes. Their expression is commonly regulated by DNA methylation at CpG islands preceding transcription starting sites. Their proteins primarily engage in histone tail modifications through interactions with chromatin regulators (PRC2, TrxG, PR-DUB, SRC1, HP1α, and BET proteins) and with transcription factors, including nuclear hormone receptors (RAR, PPAR, ER, and LXR). Histone modifications associated with these factors include histone H3K9 acetylation and methylation, H3K4 methylation, H3K27 methylation, and H2AK119 deubiquitination. Recently, non-coding RNAs have been identified following mutations in the ASXL1 or ASXL3 gene, along with circular ASXLs and microRNAs that regulate ASXL1 expression. The diverse epigenetic regulations linked to ASXL family genes collectively contribute to tumor suppression and developmental processes. Our understanding of ASXL-regulated epigenetics may provide insights into the development of therapeutic epigenetic drugs.

Generation of rat-derived lung epithelial cells in Fgfr2b-deficient mice retains species-specific development

Regenerative medicine is a tool to compensate for the shortage of lungs for transplantation, but it remains difficult to construct a lung in vitro due to the complex three-dimensional structures and multiple cell types required. A blastocyst complementation method using interspecies chimeric animals has been attracting attention as a way to create complex organs in animals, although successful lung formation using interspecies chimeric animals has not yet been achieved. Here, we applied a reverse-blastocyst complementation method to clarify the conditions required to form lungs in an Fgfr2b-deficient mouse model. We then successfully formed a rat-derived lung in the mouse model by applying a tetraploid-based organ-complementation method. Importantly, rat lung epithelial cells retained their developmental timing even in the mouse body. These findings provide useful insights to overcome the barrier of species-specific developmental timing to generate functional lungs in interspecies chimeras.

Bohring-Opitz syndrome caused by a novel ASXL1 mutation (c.3762delT) in an IVF baby: A case report

RATIONALE

Bohring-Opitz syndrome is a severe congenital disorder associated with a de novo mutation in the additional sex combs-like 1 (ASXL1) gene, and it is characterized by symptoms that include developmental delay and musculoskeletal and neurological features.

PATIENT CONCERNS

The patient was a girl, an in vitro fertilization (IVF) baby, with delayed motor development, drooling, short stature, slow growth, low muscle tone, image diagnosis of hypoplasia of the corpus callosum, delayed tooth eruption, high palatal arch, adduction of the thumb, drooling, not chewing, excessive joint activity, and ligament relaxation.

DIAGNOSIS

Whole-exome sequencing analysis detected 1 novel disruptive frameshift mutation in ASXL1 in the proband but wild-type ASXL1 in both parents.

INTERVENTIONS

Approximately 1 year of rehabilitation training, which included exercise therapy, toy imitation operation, cognition of daily objects, daily living skills training, gesture language training, oral muscle training, and hand movement training.

OUTCOMES

After approximately 1 year of training, the patient was 3 years old and able to eat normally without drooling. She was able to grasp objects and pick them up after they fell. She was able to grasp small objects and actively played with toys. In addition, she was able to crawl on the floor (at slow speed, with poor initiative), stand with assistance, and walk with assistance; she was unstable when standing unassisted (standing unassisted for 8 seconds at most during training).

LESSON

ASXL1 c.3762delT is a novel mutation that may be caused by IVF. This finding suggests that appropriate gene mutation detection approaches may be necessary for IVF technology.