Commentary - CRISPR-based techniques: Cas9, Cas13 and their applications in the era of COVID-19

The CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 (CRISPR-associated protein 9) system enables scientists to edit diverse genome types with relative ease, with the aim - in the near future - to prevent future human beings from developing genetic diseases. The new opportunities arising from the system are broad-ranging and revolutionary, but such prospects have also been the cause for alarm throughout the international scientific community. The authors have laid out a review of the trials carried out so far in terms of genome editing, for the ultimate purpose of weighing implications and criticisms. We feel that possible valuable alternatives, such as induced pluripotent stem cells should not be overlooked.

Androgen insensitivity syndrome

OBJECTIVE

We provide a review of the literature about the Androgen Insensitivity Syndrome (AIS), its onset and associated developmental anomalies and the genetic alterations causing it.

MATERIALS AND METHODS

We searched PubMed with a larger emphasis on the physiology, genetics and current management of AIS.

RESULTS

AIS is an X-linked recessive Disorder of Sex Development (DSD). It is caused by mutations of the Androgen Receptor, and their large amount and heterogeneity (missense and nonsense mutations, splicing variants, deletions, and insertions) are responsible for the wide spectrum of possible phenotypes of patients, divided into Partial AIS (PAIS) and Complete AIS (CAIS). Once the clinical and laboratory investigations have laid the foundation for a diagnostic hypothesis, it is important to identify the actual karyotype of the individual and search for the mutation in the Androgen Receptor to diagnose with certainty the syndrome. Alternatively, in the absence of such evidence, the diagnosis should more properly be an AIS-like condition, which we describe as well in our report.

CONCLUSIONS

The management of this DSD is based on pharmacotherapies, surgery and psychological support: all of them must be directed to facilitate the patient's life, considering his/her sexual identity.

Vesicoureteral reflux in infants: what do we know about the gender prevalence by age?

OBJECTIVE

Vesicoureteral reflux (VUR) affects up to 1% of Caucasian children. Primary VUR is characterized by failure of the ureterovesicular junction to prevent urine from traveling in a retrograde fashion from the bladder to the ureters and the kidneys. Several reports in the literature describe the prevalence of this condition in pediatric patients; overall, VUR affects more males during infancy and with higher grades. However, a thorough consideration of these articles reveals important contradictions regarding the prevalence by gender and age. We analyzed those contradictions and suggested a possible explanation based on our single center experience with this patient group. In particular, for the age interval 0-2 years: we have found that (1) VUR mostly affects boys; (2) the male/female ratio steadily declines over time; (3) the unequal prevalence between males and females essentially disappears when children reach the age of two years.

CONCLUSIONS

The natural history of VUR in infant boys differs from that of infant girls, and therefore requires a gender-specific approach. Available data support the need to redefine the categorization and clinical guidelines for this disease.

Surgical management of Necrotizing Enterocolitis in an Incredibly Low Birth Weight infant and review of the Literature

Survival of preterm infants have dramatically improved over the last decades. Nonetheless, infants born preterm remain vulnerable to many complications, including necrotizing enterocolitis (NEC). The severity of the disease and the mortality rate are directly correlated with decreasing gestational age and birth weight. Despite surgical treatment mortality rate remains very high in extremely premature infants, especially in newborns at the lowest limit of viability. Survival of infants of birth weight (BW) below 750 g has been increasingly reported in recent years, however the overall mortality in extremely low "BW" infants (ELBW) requiring surgery for NEC has not decreased over the past years. We describe our experience with a male preterm infant who survived after an ileostomy procedure for Bell stage II NEC, with improving neuromotor skills at 2 years follow up. Although standard indication to surgery is Bell stage III, in our case the choice of minimal laparotomy, exploration of the bowel and ileostomy at Bell stage II was safe and effective. Our experience suggest that surgery has not a negative impact on survival and ileostomy could prevent further damage of the bowel in NEC. We hypothesize that indication to surgery at an earlier stage may prevent further progression of the disease without a significantly negative impact on survival. Further studies are needed to confirm the appropriateness of this approach in ELBW infants.

Visualization of cleavage furrow proteins in fixed dividing spermatocytes

Cytokinesis separates the cytoplasmic organelles and the duplicated genome into two daughter cells at the end of cell division. In animal cell cytokinesis, assembly and constriction of the contractile apparatus must be finely coordinated with plasma membrane remodeling and vesicle trafficking at the cleavage furrow. Accurate control of these events during cell cleavage is a fundamental task in all organisms and is also essential for maintaining ploidy and preventing neoplastic transformation. Drosophila male meiosis provides a well-suited cell system for exploring the molecular mechanisms underlying cytokinesis, combining the powerful tools of Drosophila genetics with unique cytological characteristics. Remarkably the large size of male meiotic cells highly facilitates cytological analysis of cytokinesis. Here we describe the main procedures that we use for fixing and visualizing cleavage furrow proteins in male meiotic cells. Moreover, we detail our protocol to detect protein interactions in fixed dividing spermatocytes by applying in situ proximity ligation assay.

Hypersensitivity to camptothecin in MSH2 deficient cells is correlated with a role for MSH2 protein in recombinational repair

DNA mismatch repair (MMR) corrects DNA polymerase insertion errors that have escaped proofreading in order to avoid the accumulation of deleterious mutations. While the role of MMR in the correction of replication errors is well established, its involvement in the processing of DNA damage induced by chemical and physical agents is less clear. A role for some of the MMR proteins, such as MSH2, in the repair of double strand break (DSBs) through recombination has also been envisaged. Why MMR- deficient cells are sensitive to agents causing replication fork stalling and thus DSBs remains unclear. To verify a possible role of MSH2 in homologous recombinational repair, we have treated cells from knockout mice for the MSH2 gene and mouse colorectal carcinoma cells also defective for MSH2 with different doses of camptothecin, an agent known to interfere with DNA replication. In the absence of MSH2, we found a reduced survival rate accompanied by higher levels of chromosomal damage and SCE induction. Furthermore, MSH2(-/-) cells displayed an elevated spontaneous RAD51 focus-forming activity and a higher induction of RAD51 foci following camptothecin treatment. Thus, the absence of MSH2 could result in both spontaneous DNA damage and uncontrolled recombination events leading to the observed higher yield of chromosomal damage and the higher induction of RAD51 foci following CPT treatment. Therefore, our results suggest an involvement of MSH2 in the early events leading to correct RAD51 relocalization after the formation of DSBs specifically produced at the blocked replication fork.

On the origin of metacentric, attached-X (A-X) chromosomes in Drosophila melanogaster males

We describe here the isolation and cytogenetic characterization of a mutation inseparabile which generates in males a high frequency of A-X females. The mutation, segregating in low frequency in a laboratory stock, maps to cytological location 82F7-11 in the third chromosome. The mutation acts premeiotically in the male germ line. Disrupting the X chromosome centromeric heterochromatin suppresses the formation of A-X chromosome, implying that the mutation is involved in chromatid cohesion. The inseparabile mutation also affects disjunction of the chromosome 4 in males. We suspect that the mutation was responsible for the original A-X female found by L. V. Morgan in 1921.