Si le terme amélioration humaine, human enhancement, est utilisé depuis maintenant plusieurs décennies (1), l’OMS (Organisation Mondiale pour la Santé) vient d’en donner une version actualisée, dans le cadre de ses recommandations pour la gouvernance du genome editing, edition du génome (1). Au delà de la traditionnelle question de la limite entre les pratiques qui relèvent de la santé et les pratiques qui relèvent de l’amélioration, sept cas hypothétiques, imaginés et commentés par l’OMS, dessinent les contours de de l’amélioration humaine à l’heure du genome editing et de CRISPR-Cas9. On y relève en particulier :

• Une réflexion sur de nouvelles technologies basées sur l’épigénétique, avec le cas “Proposed use of somatic or epigenetic genome editing to enhance athletic performance ». “Epigenetic editing research is moving very quickly. A recent important advance could substantially change both the range of uses and the harm–benefit profile of epigenetic editing, through the use of a CRISPRoff tool, which allows scientists to switch off almost any gene in human cells without making a single edit to the genome sequence. The change would persist but could be reversed with the complementary CRISPRon tool » (2). La réversibilité attachée à cette technologie induira t-elle de nouvelles réflexions dans le domaine de l’amélioration des capacités humaines, se demandent notamment les auteurs du rapport.
• Une illustration de ce que pourrait devenir un tourisme médical appliqué aux technologies de reproduction, avec le cas ” An imaginary clinic based in a country with minimal oversight of heritable human genome editing that offers these services to international clients following in vitro fertilization and preimplantation genetic diagnosis ». Instruits par les activités du Dr Jiankui, les auteurs du rapport recommandent de mettre en place une veille des usages de l’edition du génome pour des cellules germinales, ainsi qu’une collaboration internationale, afin d’anticiper des pratiques qui seraient “illegal, unregistered, unethical or unsafe ». Ils semblent laisser de coté toute idée de traité international.

Le rapport présente par ailleurs une très interessante et impressionnante synthèse des applications potentielles des technologies d’édition du génome, actuelles, potentielles et spéculatives (3) :

“To alter genes or their activity in: (i) human somatic cells or tissues (including organoids), or germline cells (zygotes, early embryos, pluripotent stem cells, embryo models, germ cells, spermatogonial stem cells, gamete precursor cells or gametes); or (ii) laboratory animals containing human genes, cells or tissues.
• To study human biology and the role of specific genes and processes in, for example, development, physiology and disease.
• To establish a models of human genetic disease.
• To screen for human genes that are involved in disease or that respond to substances, including potential therapeutic agents and toxic materials.
• To refine techniques of genome editing and test specific reagents for use in somatic and germline human genome editing.

To treat genetic disorders: to alter genes or their activity ex vivo (e.g. using bone marrow stem cells) or in vivo (e.g. using viral vectors).
• To treat monogenic disorders by: (i) correcting the mutant allele for autosomal recessive, sex chromosome-linked or dominant
mutations in nuclear DNA or by correcting or eliminating mutant mitochondrial DNA; (ii) deleting the disease-causing variant for dominant mutations (e.g. for Huntington disease) or making deletions to promote exon skipping (e.g. for Duchenne muscular dystrophy); (iii) by boosting the expression of a closely related homologue through inactivating genes encoding repressors or by mutating repressor regulatory elements (e.g. to boost gamma globin gene expression for sickle-cell disease or beta-thalassaemia); or (iv) by using so-called safe harbour sites in the genome to integrate a gene whose expression will rescue a loss-of-function mutation (e.g.one leading to an enzyme deficiency).
• To boost an immune response against cancer cells (e.g. via chimeric antigen receptor (CAR) Tcells).
• To correct somatic mutations in stem cells leading to disease (e.g. acute mye loid leukaemia and chronic lymphocytic leukaemia).
• To treat polygenic disorders or disorders influenced by both genes and environment (e.g. coronary heart disease, cancer and auto
immune diseases).

To avoid inheritance of genetic disorders.
• To correct the mutant allele for monogenic disorders including autosomal recessive, sex chromosome-linked or dominant mutations in nuclear DNA or by correcting or eliminating mutant mitochondrial DNA.
• To reduce the likelihood of complex, multifactorial or polygenic disorders (e.g. coronary heart disease, diabetes and auto immune diseases).

To treat infertility.
• To alter genes in gonadal supporting cells, such as Sertoli or granulosa cells, so that the germ cells can form functional sperm or oocytes.
• To correct mutations in germ cells in the testes or ovaries, or in germ line cells used to derive gametes in vitro.

To promote disease resistance: to alter an allele associated with increased risk of a disease or disorder to one that is protective.
• To reduce infectious diseases and parasites, for example, by altering human genes encoding pathogen receptors or that
allow pathogen replication (e.g. CC 5 for HIV).
• To reduce cancers due to (i) oncogene activation or(ii tumour suppressor mutations (which can involve lossof heterozygosity,
e.g. BRCA1 gene).
• To reduce genetic diseases influenced by known genetic risk factors/alleles (e.g. Alzheimer disease and APOE4 versus APOE2 or APOE3).

To improve robustness or quality of life: To alter an allele that may be relatively rare or common to a different common allele.
• To increase tolerance to, for example, lactose, gluten or alcohol (e.g. improve diet).
• To reduce blood cholesterol levels (e.g.improve metabolism).
• To avoid adverse drug events or promote better therapy (e.g.so-called reverse pharmacogenomics).

To add non-human traits: To introduce single or multiple genes not present in any human genome (e.g. non-human or synthetic genes).
• To amuse/entertain (e.g. green fluorescent protein).
• To improve sensory systems (e.g.to ultraviolet or infrared light, or electromagnetic fields).
• To obtain nutritional benefit from parts of plants plastics and other materials that humans cannot currently digest.
• To increase tolerance to drought, heat or cold.
• To provide resistance to pollutants or other environmental agents such as radiation.

To enhance human traits: To alter alleles to other variants, which may be common or rare (and give extreme characteristics), that are present within the family or in other human populations.
• To alter appearance (e.g. eye or hair colour).
• To alter abilities (e.g. muscle mass or perfect pitch).
• To increase muscle type, height, longevity or intelligence.
• To provide resistance to pollutants or other environmental agents such as radiation”.

1 – Simone Bateman, Jean Gayon. L’amélioration humaine, trois usages, trois enjeux. Médecine/Sciences. Octobre 2012. https://doi.org/10.1051/medsci/20122810019

2 – Human Genome Editing. A  framework for gouvernance, page 25. https://www.who.int/publications/i/item/9789240030060 

3  – Human Genome Editing. A  framework for gouvernance, page 6. https://www.who.int/publications/i/item/9789240030060

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