Mie University Breakthrough: CRISPR Removes Extra Chromosome 21 in Down Syndrome Cells

Understanding Down Syndrome and Trisomy 21

Down syndrome, also known as trisomy 21, is a genetic condition caused by the presence of an extra copy of chromosome 21 in a person's cells. This chromosomal abnormality leads to a range of physical, developmental, and intellectual challenges. In Japan, the prevalence stands at approximately 22 per 10,000 births, higher than many other countries due to cultural attitudes toward prenatal screening and selective termination. 84 68 Individuals with Down syndrome often face complications such as congenital heart defects, hearing loss, thyroid issues, and an increased risk of Alzheimer's disease later in life. Early intervention and lifelong support are crucial, yet no treatment has addressed the root cause—the extra chromosome—until recent advancements.

The condition affects about 1 in 700 live births globally, translating to thousands of cases annually in Japan alone. Support systems in the country include specialized education programs and medical care, but research into curative therapies has accelerated with tools like gene editing.

Mie University's Pioneering Publication in PNAS Nexus

In February 2025, researchers from Mie University Graduate School of Medicine published a landmark study in PNAS Nexus titled "Trisomic rescue via allele-specific multiple chromosome cleavage using CRISPR-Cas9 in trisomy 21 cells." Led by Lecturer Ryotaro Hashizume from the Department of Genomic Medicine, the team demonstrated for the first time the targeted removal of the extra chromosome 21 from human cells derived from Down syndrome patients. 81 80 This proof-of-concept work marks a significant milestone in Japanese higher education's contributions to genomic medicine.

The study utilized patient-derived induced pluripotent stem (iPS) cells and fibroblasts, showcasing the technique's versatility across cell types. Mie University's press release highlighted its potential to pave the way for therapies addressing the fundamental genetic cause of Down syndrome. 9

🔬 The Science Behind CRISPR-Cas9 Chromosome Editing

CRISPR-Cas9, or Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9, is a revolutionary gene-editing tool derived from bacterial immune systems. It allows precise cuts in DNA at targeted locations guided by customizable RNA sequences.

In this Mie University study, the team employed an allele-specific approach to distinguish the extra chromosome 21 from the two normal ones. They designed guide RNAs targeting unique single nucleotide polymorphisms (SNPs) on the duplicated chromosome. Multiple Cas9 cuts fragmented the target chromosome, leading to its loss during cell division. Here's how it works step-by-step:

• Design phase: Identify allele-specific sequences unique to the extra chromosome using proprietary extraction methods.
• Delivery: Introduce CRISPR components via electroporation into trisomy 21 cells.
• Cleavage: Cas9 induces multiple double-strand breaks on the target chromosome.
• Loss induction: Temporary knockdown of DNA repair genes like TP53BP1 boosts chromosome elimination rates to 37.5%.
• Verification: FISH (fluorescence in situ hybridization) confirms disomy restoration.

This method's innovation lies in its specificity, avoiding off-target effects on normal chromosomes. 79

Key Results: Achieving Up to 37.5% Karyotype Correction

The research achieved remarkable efficiency: in trisomy 21 iPS cells, 30.6% to 37.5% of edited cells regained normal disomy 21 after selection. Fibroblasts, which are differentiated and non-dividing, also showed successful rescue, expanding potential applications.

Post-editing, rescued cells exhibited normalized gene expression profiles, with overexpression of chr21 genes reduced to euploid levels. Cell proliferation rates matched wild-type cells, and antioxidant capacity improved, mitigating oxidative stress—a common Down syndrome phenotype.

Importantly, the reversibility was demonstrated: reintroducing chr21 genes mimicked trisomy effects, confirming the causal link. 102 Explore the full PNAS Nexus paper for detailed figures. 17

Led by Ryotaro Hashizume: Expertise Driving Innovation

Lecturer Ryotaro Hashizume, specializing in pathology, genetics, and regenerative medicine, heads Mie University's efforts in chromosome manipulation. His background includes advanced training and a focus on clinical translation of genomic tools. This project builds on his prior work in genome analysis and CRISPR applications.

Mie University's Genomic Medicine unit provides a fertile ground for such research, supported by national initiatives like Japan's genome editing programs. Aspiring researchers can find opportunities in research jobs at institutions like Mie, contributing to fields like personalized medicine. 115

Restoring Cellular Phenotypes: Beyond Mere Removal

The study's strength lies in functional validation. Rescued cells showed:

• Normalized proliferation: No longer slowed by trisomy-induced stress.
• Balanced gene dosage: Chr21 genes like APP and SOD1 returned to euploid expression.
• Improved resilience: Enhanced resistance to oxidative damage.

These changes suggest potential for therapeutic mosaicism—partial correction in somatic cells could alleviate symptoms without full-body editing.

Implications for Down Syndrome Treatment in Japan

While still preclinical, this Mie University breakthrough opens doors to in vivo applications, perhaps via targeted delivery to neural or cardiac tissues. In Japan, where Down syndrome support is robust but curative options limited, it could reduce complication rates like dementia (prevalent after age 40).

Link to Mie University's official press release for more. 81 Careers in genomic therapy are booming; check higher ed research jobs in Japan.

Ethical Considerations and Stakeholder Perspectives

The research sparked debate. The Japan Down Syndrome Association (JDS) submitted a statement to Mie University, praising the science but critiquing the press release's language for implying Down syndrome births are undesirable and exaggerating support needs. They urged sensitive communication. 123

Globally, eugenics concerns arise, but proponents emphasize symptom relief for existing individuals. Japan's regulations on CRISPR remain permissive for somatic editing, with ethics boards overseeing trials. Balanced views highlight informed consent and equitable access.

Mie University's Place in Japanese Higher Ed Research

Mie University exemplifies Japan's push in genomic medicine, backed by MEXT funding and centers like the Research Center for Genomic Medicine. This aligns with national goals to lead in regenerative tech. For faculty positions, visit professor jobs or Japan university opportunities.

Future Outlook: From Cells to Clinical Trials

Next steps include animal models and safety optimizations. Mie researchers aim for higher efficiency and delivery vectors like AAV. Collaborations with Tokyo U and Kyoto U could accelerate progress. Long-term, this could transform Down syndrome management worldwide.

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Photo by Johannes Waibel on Unsplash

Career Opportunities in Japan's Genomics Field

This breakthrough underscores demand for experts in gene editing. Mie University and peers seek postdocs and lecturers. Browse postdoc jobs, research assistant roles, and university jobs in Japan. Platforms like Rate My Professor offer insights into faculty life.