Tephritid flies, also known as true fruit flies, are medium-sized flies that have characteristic banding or star-shaped patterns on their wings. Some species have hyaline wings. They are found throughout the world, particularly in temperate and tropical regions.
Tephritids can be divided into two broad categories: fruit-infesting and non-fruit infesting species. The fruit infesting species, such as the Mediterranean fruit fly, are considered serious pests as their larvae feed and damage fruits. The non-frugivorous species include mainly the flower-head infesting species, and these are flies that exploit wild plants, such as thistles.
Female tephritids place their eggs using their ovipositor (egg-laying tube) within the flower heads of their host. The eggs hatch into larvae that feed and destroy few seeds, hence, reducing the reproductive capacity and density of its plant host and contributing to natural balance. For this reason, many of the flower-head tephritids have been used in the biological control of invasive weeds.
Tephritd flies are highly adapted to the phenology of their host plants. They exhibit host shifts which can lead to rapid race formation. Consequently, they have been used as models to study sympatric speciation (speciation without geographical or physical barrier separating a population).
In Lebanon, our survey on the flower-head infesting tephritids revealed the existence of 18 species associated with 20 species of thistles (Family Asteraceae; Tribe Cardueae). Among the identified species, Chaestostomella cylindrica behaved as generalist infesting the flower heads of ten species of thistles.
Chaetostomella cylindrica commonly exploits in Lebanon the flower heads of two hosts, Notobasis syriaca and Onopordum species. The two thistle species occur in sympatry and bloom in May-June. The flies associated with Notobasis had darker spots on their thorax than those reared from Onopordum. The immature stages (larvae and pupae) from the two host-associated populations were similar; however, they were significantly larger in the Onopordum-associated race, reflecting the larger flower head size of their host plant.
Females from both host plants differed in the length and shape of the ovipositor (egg-laying tube). Females associated with the relatively smaller flower heads of Notobasis had a shorter ovipositor with a pointed tip while those associated with the larger Onopordum heads had a longer ovipositor with a blunt tip. Hence, the ovipositor morphology was highly adapted to the size and shape of the exploited flower head.
Ovipositor of Chaetostomella cylindrica females from (A) the Notobasis associated host race and (B) the Onopordum associated host race. Bar = 0.5 mm.
Molecular studies based on sequencing the mitochondrial NADH-dehydrogenase subunit 1 gene showed the existence of two genetically distinct lineage with a difference of 44 single nucleotide polymorphisms in 622 base pairs. This demonstrates that the two host races exhibit very little or no gene flow. They could be considered different sympatric species as they had 7.1% sequence divergence.
Mitochondrial DNA sequencing showed the existence of two genetically distinct lineages NADH gene showed that C. cylindrica consists of a complex of cryptic and reproductively isolated species found in sympatry (same geographical areas). Similar studies on T. serratulae revealed the existence of distinct host races. Host races are populations of the same species that show preference and adaptation to a specific, sometimes new plant host, and that exhibit some genetic and morphological differences. They are considered as an intermediate step that leads to speciation.
In conclusion, Chaetostomella cylindrica seems to consist of cryptic and distinct host races.
Cancer remains a serious global health issue that inflicts suffering on millions each year. Multiple areas of cancer research have been invested into and studied over numerous decades, and yet vast amounts of contemporary drugs on the market fail to treat cancer adequately, nearly always due to imprecision, possible substantial toxicity, or limited efficacy — due largely to individual tumor differences. However, an innovative wave of tools is emerging to provide new hope.
CRISPR and PROTACs are two revolutionary technologies that will likely change the way we approach the study of cancer, leading to precision therapies that are different for individual patients. Dr. Diana Jaalouk and her lab in the Department of Biology at the American University of Beirut are conducting research utilizing CRISPR and PROTACs to develop new insight and approaches to targeting cancer at the source.
Gene Editing with CRISPR: Precision When Targeting DNA
CRISPR-Cas9 has often been touted as one of the most powerful genetic tools ever discovered. Often described as “molecular scissors”, CRISPR-Cas9 has facilitated researchers to cut and modify human DNA with unprecedented precision. Originally discovered as part of a bacterial defense mechanism, CRISPR-Cas9 can be employed to directly edit human cells by modifying cancer-causing human mutations.
Researchers are utilizing CRISPR to target KRAS mutations in lung cancer, or TP53 mutations in breast cancer — gene alterations that represent drivers of tumor biologic growth. Not only are researchers employing CRISPR to edit DNA, they can also enhance cancer targeted therapies. Researchers manipulated immune cells, like T-cells to better recognize and kill cancer cells and have made significant strides. Preliminary clinical trials indicate that T-cells modified with CRISPR to remove the PD-1 gene—enhancing the immune response—are safe and potentially efficacious for treatment of non-small-cell lung cancer.
PROTACs: Destroying Oncogenic Proteins
While CRISPR operates at the level of the gene, PROTACs (short for PROteolysis TArgeting Chimeras) operate at the level of the protein, which is the output of DNA. These small molecules serve as a type of "tag-and-kill" cleanup crew, identifying potentially harmful proteins for destruction by the cell's native waste management system.
The capacity of PROTACs to target proteins that are otherwise thought to be "undruggable," is another noteworthy consideration. For example, BRD4—an undesired protein associated in aggressive cancers like leukemia—is often reported as a promising target. Using a PROTAC molecule called dBET1, scientists have degraded BRD4 by >85% in vitro, while inhibiting proliferation of cancer cells. In vivo efficacy has also been demonstrated, whereby enduring tumor regression occurred with minimal side effects.
PROTACs are undergoing clinical evaluation in prostate and breast cancers; especially in patients who have become resistant to conventional cancer therapies. Important to note: Because PROTACs aim to destroy the target protein instead of simply blocking it with a drug, PROTACs often take effect at a much smaller dose, thus leading to reduced drug toxicity and an enhanced quality of life for patients.
A Powerful Combination
CRISPR and PROTACs are powerful tools by themselves. But together, they could be game changers. CRISPR for turning off or fixing the malfunctioning genes, and PROTACs for targeting the malfunctioning proteins. This combination could be beneficial in tackling malignancies that are resistant to standard drug therapies, and it may decrease the risks of recurrent cancers. Dr. Jaalouk explains that the two technologies don't compete with one another, they are rather complementary and can be used in combination to develop treatments that are individualized to each patients tumor profile, hence may be bring us closer to a future when precision medicine while not the norm, isn't the exception.
However, both technologies face their own challenges. The most significant challenge for CRISPR is off-target effects, or unintended alterations to normal genes that can lead to side-effects. The issue for PROTACs is simply to ensure that only the target proteins are the proteins that are degraded. Researchers are utilizing advanced computer modeling as well as other innovative screening modalities, to increase precision and decrease side-effects.
The second complication is for the therapy to be delivered. It is suiting chemicals into the right cells, without killing other cells is not straightforward. Nanoparticles, and viral delivery systems, are some of the potential methodologies being developed, to safely deliver CRISPR and PROTACs to their targets.
Another important consideration is the immune system. These medications can trigger immune responses that limit their effectiveness. To remedy this, some researchers are developing methods to "cloak" these therapies; thereby, programming with the immune system to help defend against these the body's immune system, while still enabling the therapy to work.
Nevertheless, the momentum of CRISPR and PROTACs is clear, and the innovation around both technologies is accelerating us toward the dream of highly personalized, effective, and a less toxic way to treat cancer: CRISPR has already shown that it is possible to fix the genetic mutations that cause cancer, and PROTACs are showing that it is possible to eliminate the proteins that maintain the cells viability. So while this is better than a single function from CRISPR or PROTAC, the combination is even better.
This line of research illustrates the possibilities that emerge when innovative science informs clinical need. If trends continue, it is possible that precision oncology will one day turn cancer into a curable disease.
The following SciPod is a summary of the paper ‘Precision oncology revolution: CRISPR-Cas9 and PROTAC technologies unleashed’, published in Frontiers in Genetics,
https://doi.org/10.3389/fgene.2024.1434002
For further information, you may connect with Dr. Diana Jaalouk at
[email protected]