Synthetic gene circuits for cell state detection and protein tuning in human pluripotent stem cells.

During development, cell state transitions are coordinated through changes in the identity of molecular regulators in a cell type- and dose-specific manner. The ability to rationally engineer such transitions in human pluripotent stem cells (hPSC) will enable numerous applications in regenerative medicine. Herein, we report the generation of synthetic gene circuits that can detect a desired cell state using AND-like logic integration of endogenous miRNAs (classifiers) and, upon detection, produce fine-tuned levels of output proteins using an miRNA-mediated output fine-tuning technology (miSFITs). Specifically, we created an "hPSC ON" circuit using a model-guided miRNA selection and circuit optimization approach. The circuit demonstrates robust PSC-specific detection and graded output protein production. Next, we used an empirical approach to create an "hPSC-Off" circuit. This circuit was applied to regulate the secretion of endogenous BMP4 in a state-specific and fine-tuned manner to control the composition of differentiating hPSCs. Our work provides a platform for customized cell state-specific control of desired physiological factors in hPSC, laying the foundation for programming cell compositions in hPSC-derived tissues and beyond.

Frequency of allele variations in the CFTR gene in a Mexican population.

BACKGROUND: Cystic fibrosis (CF) is an autosomal recessive disorder caused by pathogenic variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The CF variants incidence is highly variable and even undetermined in some countries like Mexico. METHODS: In this study, the allele frequencies of 361 variants in the CFTR gene were investigated in 1455 Mexicans without a CF or CFTR-related disorders (CFTR-RD) diagnosis. We also performed a statistical comparative analysis against allele frequencies of different populations to measure genetic differences in the prevalence of CFTR variants. RESULTS: In the vast majority of cases, the allele frequencies of this cohort were comparable to those found in other populations. However, some variants displayed significant differences in their allele frequencies when compared with European and African populations. CONCLUSIONS: This study provides information about CFTR variants to predict the prevalence of CF in Mexico and uncover other unknown but frequent pathogenic variants in the country. Additionally, other CFTR-RD variants have also been studied using population data of the same CFTR variants. Studies like this could help develop a regional molecular diagnostic screen to optimize the medical care of CF patients.

Clinical Characterization of 2 Siblings with a Homozygous SPAST Variant.

BACKGROUND Hereditary spastic paraplegia (HSP or SPG) consists of a heterogeneous group of disorders, clinically divided into pure and complex forms. The former is characterized by neurological impairment limited to lower-extremity spasticity. The latter presents additional symptoms such as seizures, psychomotor impairment, cataract, deafness, and peripheral neuropathy. The genetic structure of HSP is diverse, with more than 72 loci and 55 genes identified so far. The most common type is SPG4, accounting for 40% of cases. This case report describes 2 siblings presenting SPG4, one presumptive and one confirmed with a homozygous SPAST variant. CASE REPORT Two siblings born to third-degree consanguineous and healthy parents presented a SPG4 complex phenotype characterized by progressive psychomotor deterioration, mixed seizure patterns, corneal opacity, dysostotic bones, limb spasticity with extensor plantar responses, and axial hypotonia. After ruling out most inborn errors of metabolism in one of the patients, the complexity of the case derived from exome sequencing. The identification of a homozygous variant in the SPAST gene established a diagnosis for SPG4. The phenotype-genotype did not correlate to classical manifestations, most likely due to the variant's zygosity. Moreover, 34 patient's relatives were identified with SPG4 clinical manifestations or asymptomatic with the same genetic variant in heterozygous state. CONCLUSIONS We described visual loss and seizures for SPG4 complex phenotype associated with a homozygous variant in the SPAST gene. This diagnosis will lead clinicians to consider it as a differential diagnosis providing adequate genetic counseling.

Incidence of Inborn Errors of Metabolism by Expanded Newborn Screening in a Mexican Hospital

Abstract Newborn screening for the detection of inborn errors of metabolism (IEM), endocrinopathies, hemoglobinopathies, and other disorders is a public health initiative aimed at identifying specific diseases in a timely manner. Mexico initiated newborn screening in 1973, but the national incidence of this group of diseases is unknown or uncertain due to the lack of large sample sizes of expanded newborn screening (ENS) programs and lack of related publications. The incidence of a specific group of IEM, endocrinopathies, hemoglobinopathies, and other disorders in newborns was obtained from a Mexican hospital. These newborns were part of a comprehensive ENS program at Ginequito (a private hospital in Mexico), from January 2012 to August 2014. The retrospective study included the examination of 10 000 newborns' results obtained from the ENS program (comprising the possible detection of more than 50 screened disorders). The findings were the following: 34 newborns were confirmed with an IEM, endocrinopathies, hemoglobinopathies, or other disorders and 68 were identified as carriers. Consequently, the estimated global incidence for those disorders was 3.4 in 1000 newborns; and the carrier prevalence was 6.8 in 1000. Moreover, a 0.04% false-positive rate was unveiled as soon as diagnostic testing revealed negative results. The most frequent diagnosis was glucose-6-phosphate dehydrogenase deficiency; and in the case of carriers, it was hemoglobinopathies. The benefit of the ENS is clear as it offers prompt treatment on the basis of an early diagnosis including proper genetic counseling. Furthermore, these results provide a good estimation of the frequencies of different forms of newborn IEM, endocrinopathies, hemoglobinopathies, and other disorders at Ginequito.