Differential sialic acid content in adult and neonatal fibrinogen mediates differences in clot polymerization dynamics

Neonates possess a molecular variant of fibrinogen, known as fetal fibrinogen, characterized by increased sialic acid, a greater negative charge, and decreased activity compared to adults. Despite these differences, adult fibrinogen is used for treatment of bleeding in neonates, with mixed efficacy. In order to determine safe and efficacious bleeding protocols for neonates, more information on neonatal fibrin clot formation and the influence of sialic acid on these processes is needed. Here, we examine the influence of sialic acid on neonatal fibrin polymerization. We hypothesized that the increased sialic acid content of neonatal fibrinogen promotes fibrin B:b knob hole interactions and consequently influences the structure and function of the neonatal fibrin matrix. We explored this hypothesis through analysis of structural properties and knob:hole polymerization dynamics of normal and desialylated neonatal fibrin networks and compare to those formed with adult fibrinogen. We then characterized normal neonatal fibrin knob:hole interactions by forming neonatal and adult clots with either thrombin or snake-venom thrombin like enzymes (SVTLEs) that preferentially cleave fibrinopeptide A or B. We determined that sialic acid content of neonatal fibrinogen is a key determinant of resulting clot properties. Experiments analyzing knob:hole dynamics indicated typical neonatal fibrin clots are formed with the release of more fibrinopeptide B and less fibrinopeptide A than adults. After the removal of sialic acid, fibrinopeptide release was roughly equivalent between adults and neonates indicating the influence of sialic acid on fibrin neonatal fibrin polymerization mechanisms. These results could inform future studies developing neonatal specific treatments of bleeding.

Accessing Targeted Therapies: A Potential Roadblock to Implementing Precision Oncology?

PURPOSE: Advances in genomic techniques have led to increased use of next-generation sequencing (NGS). We evaluated the extent to which these tests guide treatment decisions. METHODS: We developed and distributed a survey assessing NGS use and outcomes to a survey pool of ASCO members. Comparisons between groups were performed with Wilcoxon two-sample, chi-square, and Fisher's exact tests. RESULTS: Among 178 respondents, 62% were male, 54% White, and 67% affiliated with academic centers. More than half (56%) indicated that NGS provided actionable information to a moderate or great extent. Use was highest (median ≥ 70% of cases) for lung and gastric cancer, and lowest (median < 25% of cases) in head and neck and genitourinary cancers. Approximately one third of respondents reported that, despite identification of an actionable molecular variant, patients were sometimes or often unable to access the relevant US Food and Drug Administration–approved therapy. When NGS did not provide actionable results, individuals reporting great or moderate guidance overall from NGS in treatment recommendations were more likely to request the compassionate use of an unapproved drug ( P < .001), enroll on a clinical trial ( P < .01), or treat off-label with a drug approved for another indication ( P = .02). CONCLUSION: When NGS identifies an actionable result, a substantial proportion of clinicians reported encountering challenges obtaining approved therapies on the basis of these results. Perceived overall impact of NGS appears associated with clinical behavior unrelated to actionable NGS test results, including pursuing off-label or compassionate use of unapproved therapies or referring to a clinical trial.

Differential effects of RASA3 mutations on hematopoiesis are profoundly influenced by genetic background and molecular variant

Studies of the severely pancytopenic scat mouse model first demonstrated the crucial role of RASA3, a dual RAS and RAP GTPase activating protein (GAP), in hematopoiesis. RASA3 is required for survival in utero; germline deletion is lethal at E12.5–13.5 due to severe hemorrhage. Here, conditional deletion in hematopoietic stem and progenitor cells (HSPCs) using Vav-iCre recapitulates the null phenotype demonstrating that RASA3 is required at the stem and progenitor level to maintain blood vessel development and integrity and effective blood production. In adults, bone marrow blood cell production and spleen stress erythropoiesis are suppressed significantly upon induction of RASA3 deficiency, leading to pancytopenia and death within two weeks. Notably, RASA3 missense mutations in two mouse models, scat (G125V) and hlb381 (H794L), show dramatically different hematopoietic consequences specific to both genetic background and molecular variant. The mutation effect is mediated at least in part by differential effects on RAS and RAP activation. In addition, we show that the role of RASA3 is conserved during human terminal erythropoiesis, highlighting a potential function for the RASA3-RAS axis in disordered erythropoiesis in humans. Finally, global transcriptomic studies in scat suggest potential targets to ameliorate disease progression.

Differential Effects of RASA3 Mutations on Hematopoiesis are Profoundly Influenced by Genetic Background and Molecular Variant

Studies of the severely pancytopenic scat mouse model first demonstrated the crucial role of RASA3, a dual RAS and RAP GTPase activating protein (GAP), in hematopoiesis. RASA3 is required for survival in utero; germline deletion is lethal at E12.5-13.5 due to severe hemorrhage and decreased fetal liver erythropoiesis. Conditional deletion in hematopoietic stem and progenitor cells (HSPCs) using Vav-Cre recapitulates the null phenotype demonstrating that RASA3 is required at the stem and progenitor level to maintain blood vessel development and integrity and effective blood production. In adults, bone marrow blood cell production and spleen stress erythropoiesis are suppressed significantly upon induction of RASA3 deficiency, leading to pancytopenia and death within two weeks. Notably, RASA3 missense mutations in mouse models scat (G125V) and hlb381 (H794L) show dramatically different hematopoietic consequences specific to both genetic background and molecular variant. Global transcriptomic studies in scat suggest potential targets to ameliorate disease progression.Author SummaryHematopoiesis is the process by which blood cells are formed. The individual must have a normal complement of red blood cells to prevent anemia, platelets to control bleeding, and white blood cells to maintain immune functions. All blood cells are derived from hematopoietic stem cells that differentiate into progenitor cells that then develop into mature circulating cells. We studied several mouse strains carrying different mutations in RASA3. We show that RASA3 is required at the earliest stages of blood formation, the stem and progenitor cells, and that the complement of genes other than RASA3, or the genetic background of the mutant strain, profoundly alters the overall effect on blood formation. Further, the molecular nature of the mutation in RASA3 also has a profound and independent effect on overall blood formation. One strain, designated scat, suffers cyclic anemia characterized by severe anemic crisis episodes interspersed with remissions where the anemia significantly improves. Comparison of scat crisis and remission hematopoietic stem and progenitor cells reveals striking differences in gene expression. Analyses of these expression differences provide clues to processes that potentially drive improvement of anemia in scat and provide new avenues to pursue in future studies to identify novel therapeutics for anemia.

Pitt–Hopkins syndrome with electrical stat us epileptic us in slo w-wave sleep: a case report

Pitt–Hoppkins syndrome is rare genetic disorder caused by a molecular variant of TCF4 which is involved in embryologic neuronal differentiation. The syndrome is characterized by specific facial dysmorphism, phychomotor delay, autistic behavior and intellectual disability. Other associated features include ealy-onset myopia, seizures, constipation and hyperventilation-apneic spells. We introduced a clinical case of the patient with molecularly confirmed TCF4 variant and previously undescribed combination with syndrome of the electrical status epilepticus during sleep.

Pitt-Hopkins Syndrome: A Review of Current Literature, Clinical Approach, and 23-Patient Case Series

Pitt-Hopkins syndrome (PTHS) is a rare, genetic disorder caused by a molecular variant of TCF4 which is involved in embryologic neuronal differentiation. PTHS is characterized by syndromic facies, psychomotor delay, and intellectual disability. Other associated features include early-onset myopia, seizures, constipation, and hyperventilation-apneic spells. Many also meet criteria for autism spectrum disorder. Here the authors present a series of 23 PTHS patients with molecularly confirmed TCF4 variants and describe 3 unique individuals. The first carries a small deletion but does not exhibit the typical facial features nor the typical pattern of developmental delay. The second exhibits typical facial features, but has attained more advanced motor and verbal skills than other reported cases to date. The third displays typical features of PTHS, however inherited a large chromosomal duplication involving TCF4 from his unaffected father with somatic mosaicism. To the authors’ knowledge, this is the first chromosomal duplication case reported to date.

Molecular Technologies and Test Issues

Molecular genetic testing has been around since the discovery and offering of clinical testing for the first gene sequenced. However, in recent years the methods and scope of molecular genetic testing have evolved significantly to encompass next-generation sequencing, multigene panels, and whole exome and genome testing. With this evolution in molecular methods, the nomenclature and variant evaluation and annotation processes are crucial for the systematic and standard interpretation of molecular test results. This chapter will provide the laboratory genetic counselor with information about the common sample types analyzed by molecular techniques for the purposes of genetic testing and the various methodologies available and their limitations. Guidelines are given for the standard approach to molecular variant reporting with respect to nomenclature and variant classification.