News & views
Since the last time we ran this course – we have been tracking the appearance of genomics in the news in order to assess how salient it is in the ever-changing news cycle.
It has surprised even us how frequently genomics news stories appear. Almost daily we hear about the impact of genomics on healthcare and how gene-directed diagnosis and therapies are transforming our understanding of widely divergent fields of medicine.
We thought we would share with you some of the stories we found particularly interesting. They exemplify the extent to which genomics is going to change everyone’s lives, whether as a patient or as a healthcare professional.
A Giant Leap Forward for Genome Editing
Genome editing technology has taken a significant step forward with the invention of a new form of precision genome editing, which could lead to the development of gene therapies for a much wider range of genetic diseases.
Conventional CRISPR-Cas9 editing relies on the creation of double-stranded DNA breaks at precise locations in the genome, followed by homology-directed repair using template DNA to introduce desired insertions or deletions. Whilst an extremely useful tool, it is only suitable for use on a limited range of pathogenic mutations, is inefficient in certain cell types, and may create unwanted off-target mutations.
Prime editing overcomes a number of these limitations. Instead of creating double-stranded breaks it merely ‘nicks’ a single strand of the target DNA, then uses an engineered RNA template coupled to a reverse transcriptase to directly overwrite new genetic information at the target site. This makes it much more precise and versatile than conventional genome editing technology.
The authors were able to demonstrate how this ‘search-and-replace’ capability could correct the most common genetic causes of both sickle-cell anaemia and Tay-Sachs disease in human cells, with unprecedented efficiency and few unwanted by-products. Furthermore, they claim that it could in principle correct about 89% of known human pathogenic variants, vastly expanding the potential scope of genome editing for gene therapy.
Dangers of Direct-To-Consumer Testing
Those interested in the controversy surrounding Direct-To-Consumer (DTC) genetic testing shouldn’t miss this excellent podcast from the guardian’s Hannah Devlin. She interviews Anneke Lucassen, Professor of Clinical Genetics at Southampton University, and Dr Amy Taylor, Consultant Genetic Counsellor at Addenbrooke’s Hospital, Cambridge about their experiences of the NHS ‘picking up the pieces’ after inappropriate or inaccurate DTC testing.
The sort of technology used by DTC testing companies to identify common variation, (e.g. for ancestry testing) is wholly unsuited to identifying rare pathogenic variation such as causes high penetrance Mendelian disorders. Both tell fascinating stories of patients who had DTC genetic testing which was inappropriately analysed in the private sector and resulted in false-positive results in cancer predisposition genes, creating massive anxiety amongst patients and other health professionals, and often narrowly avoiding completely inappropriate clinical management (in one case major surgery).
According to a recent piece in the MIT Technology Review, by the start of this year, more than 26 million people worldwide had taken DTC genetic tests. But with all the confusion and anxiety that can ensue when testing is done with no clinical guidance or oversight can the NHS continue to pick up the pieces, and the bill?
Where do you stand?
DNA to Catch a Killer – the Birth of DNA Fingerprinting and the State of the Art
Through today’s lens, it’s amazing to think that DNA was used for the first time for criminal forensic purposes as recently as the 1980s, and that before then DNA evidence simply did not exist.
This fascinating documentary from BBC2 recounts the birth of DNA fingerprinting by taking us back to 1986 when Leicestershire police are hunting the rapist and killer of two teenage girls from neighbouring villages.
On the basis of strong circumstantial evidence, they have a man in custody for the second murder but are unable to tie him to the first. Then the chief investigating officer remembers an article from the local paper about a new DNA identity test, developed by Dr Jeffreys at nearby Leicester University. This new technique, termed ‘DNA fingerprinting’, is able to identify people and establish their family relationships, but has never before been used for forensic purposes.
The riveting story that unfolds is of how DNA fingerprinting of the suspect and of a further 5000 local men, prevents a major miscarriage of justice and eventually leads to the identification and arrest of the serial killer.
This landmark case led to the widespread use of DNA forensics, with the subsequent development of police DNA databases. From 2004, the UK pioneered the use of ‘familial search’, where crime-scene DNA may not identify a suspect, but instead may pull up the DNA of a close relative such as a parent or sibling, leading to the identification of the suspect.
Fast forward to the present day and the state of the art is the use in the US of public-access DNA databases to track down violent criminals. Police DNA databases don’t store whole-genome sequence data, instead of focusing on repetitive regions that vary between individuals.
Crime scene DNA can be matched against a police DNA database to identify a suspect or their close relative. Public genealogy databases, however, store many more genetic data points on each individual, enabling the identification of much more distant family members.
DNA tech company Parabon has a forensic genealogy unit which uploads crime-scene DNA profiles to match to a public-access genealogy database, GEDmatch. Typically second or third cousins are identified, then there is a process of expert genealogy tracing to build the family tree and identify potential individuals who might be associated with the crime, for example by geography or social relationship.
If a likely suspect is identified, their DNA can then be tested directly against that from the crime scene.
The use of public databases for criminal forensic purposes is not without controversy. Currently, in the US, genetic data holders such as DTC testing companies may be required to give up information to the police if subpoenaed, but GEDmatch is the only public database that permits open searching by police investigating violent crime.
GEDmatch makes site-users aware that their DNA might be used for this purpose and gives them the option to remove it at any time.
Is this an ethical use of public genomic data? Where do you stand?
Which of these stories interests you most and why? Have any other stories about genomics in the press caught your eye?
© St George’s, University of London