"It's about how you take in things with your brain" - young people's perspectives on mental health and help seeking: an interview study.

INTRODUCTION: Poor mental health in young people has become a growing problem globally over the past decades. However, young people have also been shown to underutilize available healthcare resources. The World Health Organisation (WHO) has formulated guidelines for youth-friendly health services (YFHSs) to increase youth participation in healthcare. Still, little is known about how young people using these services perceive mental health, indicating a knowledge gap concerning the subjective evaluation of their mental health. AIM: To investigate how young people visiting youth health clinics (YHC) perceive the concept of mental health and factors they view as central to maintaining mental health. METHODS: In total 21 interviews were carried out, 16 in 2018, and 5 in 2023 to assure no changes in findings after the COVID-19 pandemic. Subjects were recruited during visits to youth health clinics (YHCs) in mid-Sweden and were aged 15-23 years. Recruitment strived to achieve heterogeneity in the sample concerning gender, sexual orientation, gender identity and age. Interviews were transcribed and analysed using qualitative content analysis. FINDINGS: Findings of the analysis revealed two themes, "Mental health is helped and hindered by the surroundings" and "Mental health is difficult to understand and difficult to achieve". The participants described their health as highly dependent on their social surroundings, and that these are important to maintaining health but may also affect health negatively. They described mixed experiences of the health care services and mentioned prerequisites for seeking care for mental health problems such as accessibility and respect for their integrity, including the right to turn down offered treatment. The informants also viewed mental health as an ongoing undertaking that one must work for, and that it is sometimes difficult to know what constitutes mental health. They also expressed a need from healthcare services to enquire about their health, and to show an active interest in how they are doing. CONCLUSIONS: Findings underline the need of young people's individual needs to be met in the healthcare system and their vulnerability to their social surroundings. Health status assessments in young people should consider social and individual factors to fully capture mental health.

Using Modeling All Alternatives to explore 55% decarbonization scenarios of the European electricity sector.

Climate change mitigation is a global challenge that, however, needs to be resolved by national-level authorities, resembling a "tragedy of the commons". This paradox is reflected at the European scale, as climate commitments are made by the EU collectively, but implementation is the responsibility of individual Member States. Here, we investigate a suite of near-optimal effort-sharing scenarios where the European electricity sector is decarbonized between 55% and 75% relative to 1990, in line with 2030 ambitions. To this end, we use a brownfield electricity system optimization model in combination with the Modeling All Alternatives methodology. Results show that only very particular effort-sharing schemes are able to reach the theoretical minimum system cost. In most cases, an additional cost of at least 5% is incurred. Results reveal large inequalities in the efforts required to decarbonize national electricity sectors.

Development and usability evaluation of an electronic health report form to assess health in young people: a mixed-methods approach.

BACKGROUND: Electronic Patient-Reported Outcomes (ePROs) have potential to improve health outcomes and healthcare. The development of health-technology applications, such as ePROs, should include the potential users and be theoretically grounded. Swedish Youth Health Clinics (YHCs) offer primarily sexual and psychological healthcare for young people aged 12 to 25 years old. Young people in healthcare settings are considered a vulnerable group. The development of a collection of Patient-Reported Outcomes (PROs) in an Electronic Health Report Form (eHRF) for identifying health and health-related problems in young people, was preceded by a qualitative interview study, exploring young people's views on using an eHRF at YHCs and which questions about health an eHRF should contain. The aim of the current study was to develop and evaluate the usability of an eHRF prototype for identifying health and health-related problems in young people visiting YHCs. METHODS: This study used a participatory design. During the development, an expert panel consisting of eight researchers and one Information Technology worker, participated. A wide literature search was performed to find PROs to construct an eHRF prototype to cover health areas. A mixed methods usability evaluation included 14 participants (young people, healthcare professionals, and an expert panel). RESULTS: The development resulted in an eHRF prototype, containing ten reliable and valid health questionnaires addressing mental-, physical-, and sexual health and social support, a self-efficacy question, and background questions, in total 74 items. The interviews in the usability evaluation resulted in three categories describing the usability of the eHRF: 'Captures the overall health of young people but needs clarification', 'Fun, easy, and optional and will keep young people's interest', and 'Potential contribution to improve the health consultation'. The quantitative results support the usability of the eHRF for YHCs. CONCLUSIONS: The participatory approach contributed to development of the eHRF prototype to cover health areas adapted for the target population. The usability evaluation showed that the eHRF was usable and had the potential for self-reflection and contributions to cooperation between young people and healthcare professionals during the health consultation.

Strengthening the policy framework to resolve lax implementation of the Baltic Sea Action Plan for agriculture.

In this perspective article, we provide recommendations for strengthening the policy framework for protecting the Baltic Sea from agricultural nutrient pollution. The most striking weakness is the lax implementation of prescribed abatement measures, particularly concerning manure management, in most countries. Institutions of the EU should also be leveraged for achieving Baltic Sea Action Plan (BSAP) goals. In contrast to the Helsinki Convention, the European Union has economic, political and legal mandates to further implementation and compliance. Equally important is the need for strengthening of local institutions, particularly Water Boards and independent agricultural advisory services in the eastern Baltic Sea Region countries. There is also an urgent need for implementation of voluntary land-use measures where EU funding available to farmers is more broadly and effectively used by providing it on the basis of estimated abatement performance, which can be realized through modelling. The enormous potential for funding performance-based schemes, manure management infrastructure and advisory services through the EU's Common Agricultural Policy are currently underutilized.

Promise and performance of agricultural nutrient management policy: Lessons from the Baltic Sea.

Following decades of international collaboration to restore the Baltic Sea, we provide an assessment of the domestic implementation of measures agreed to limit diffuse agricultural pollution and the patterns of policy instruments applied. Despite the Helsinki Convention being unusually specific in detailing what measures countries should introduce, we find many shortcomings. These are most pronounced in the larger countries (Poland, Germany and Russia), while smaller countries perform better, notably Sweden and Estonia. The patterns of policy instruments applied differ, influenced by domestic politics. The limited use of complementary policy instruments suggests that other priorities overrule full and effective implementation, with engagement mirroring the advantages that a restored Baltic Sea can bring to countries. Using the European Agricultural Fund for Rural Development to support farmers in managing nutrients, particularly advisory services and investments in modern manure management technologies, represents a significant opportunity for reducing agricultural pollution in most countries.

Use of novel cystine analogs to decrease oxidative stress and control product quality.

Continuous improvements of cell culture media are required in order to ensure high yield and product quality. However, some components can be instable and lead to detrimental effects on bioprocess performances. l-cysteine is an essential amino acid commonly used in cell culture media. Despite its beneficial effect on recombinant protein production, in some cases, this component can be responsible for product microheterogeneity. In this context, alternative components have to be found in order to reduce product variants while maintaining high productivity. In this study, we have assessed the performance of different cysteine and cystine analogs : N-acetyl-cysteine, s-sulfocysteine, N,N'-diacetyl-l-cystine and the N,N'-diacetyl-l-cystine dimethylester (DACDM). Replacement of cysteine by cystine analogs, and especially DACDM, has shown positive impact on charge variants level and recombinant protein coloration level. Moreover, this molecule contributed to the increase of the intracellular glutathione pool, which suggests a close relationship with the oxidative stress regulation.

Characterization of glutathione proteome in CHO cells and its relationship with productivity and cholesterol synthesis.

Glutathione (GSH) plays a central role in the redox balance maintenance in mammalian cells. Previous studies of industrial Chinese hamster ovary cell lines have demonstrated a relationship between GSH metabolism and clone productivity. However, a thorough investigation is required to understand this relationship and potentially highlight new targets for cell engineering. In this study, we have modulated the GSH intracellular content of an industrial cell line under bioprocess conditions to further elucidate the role of the GSH synthesis pathway. Two strategies were used: the variation of cystine supply and the direct inhibition of the GSH synthesis using buthionine sulfoximine (BSO). Over time of the bioprocess, a correlation between intracellular GSH and product titer has been observed. Analysis of metabolites uptake/secretion rates and proteome comparison between BSO-treated cells and nontreated cells has highlighted a slowdown of the tricarboxylic acid cycle leading to a secretion of lactate and alanine in the extracellular environment. Moreover, an adaptation of the GSH-related proteome has been observed with an upregulation of the regulatory subunit of glutamate-cysteine ligase and a downregulation of a specific GSH transferase subgroup, the Mu family. Surprisingly, the main impact of BSO treatment was observed on a global downregulation of the cholesterol synthesis pathways. As cholesterol is required for protein secretion, it could be the missing piece of the puzzle to finally elucidate the link between GSH synthesis and productivity.

A comparative genomics study of 23 Aspergillus species from section Flavi.

Section Flavi encompasses both harmful and beneficial Aspergillus species, such as Aspergillus oryzae, used in food fermentation and enzyme production, and Aspergillus flavus, food spoiler and mycotoxin producer. Here, we sequence 19 genomes spanning section Flavi and compare 31 fungal genomes including 23 Flavi species. We reassess their phylogenetic relationships and show that the closest relative of A. oryzae is not A. flavus, but A. minisclerotigenes or A. aflatoxiformans and identify high genome diversity, especially in sub-telomeric regions. We predict abundant CAZymes (598 per species) and prolific secondary metabolite gene clusters (73 per species) in section Flavi. However, the observed phenotypes (growth characteristics, polysaccharide degradation) do not necessarily correlate with inferences made from the predicted CAZyme content. Our work, including genomic analyses, phenotypic assays, and identification of secondary metabolites, highlights the genetic and metabolic diversity within section Flavi.

Chemical Diversity of Locked Nucleic Acid-Modified Antisense Oligonucleotides Allows Optimization of Pharmaceutical Properties.

The identification of molecules that can modulate RNA or protein function and the subsequent chemical and structural optimization to refine such molecules into drugs is a key activity in drug discovery. Here, we explored the extent to which chemical and structural differences in antisense oligonucleotides, designed as gapmers and capable of recruiting RNase H for target RNA cleavage, can affect their functional properties. To facilitate structure-activity learning, we analyzed two sets of iso-sequential locked nucleic acid (LNA)-modified gapmers, where we systematically varied the number and positions of LNA modifications in the flanks. In total, we evaluated 768 different and architecturally diverse gapmers in HeLa cells for target knockdown activity and cytotoxic potential and found widespread differences in both of these properties. Binding affinity between gapmer and RNA target, as well as the presence of certain short sequence motifs in the gap region, can explain these differences, and we propose statistical and machine-learning models that can be used to predict region-specific, optimal LNA-modification architectures. Once accessible regions in the target of interest have been identified, our results show how to refine and optimize LNA gapmers with improved pharmacological profiles targeting such regions.

Influence of Infant Cleft Dimensions on Velopharyngeal Function in 5-Year-Old Danish Children Born With Unilateral Cleft Lip and Palate.

AIM: To examine the association of cleft severity at infancy and velopharyngeal competence in preschool children with unilateral cleft lip and palate operated with early or delayed hard palate repair. DESIGN: Subgroup analysis within a multicenter randomized controlled trial of primary surgery (Scandcleft). SETTING: Tertiary health care. One surgical center. PATIENTS AND METHODS: One hundred twenty-five infants received cheilo-rhinoplasty and soft palate repair at age 3 to 4 months and were randomized to hard palate closure at age 12 or 36 months. Cleft size and cleft morphology were measured 3 dimensionally on digital models, obtained by laser surface scanning of preoperative plaster models (mean age: 1.8 months). MAIN OUTCOME MEASUREMENTS: Velopharyngeal competence (VPC) and hypernasality assessed from a naming test (VPC-Sum) and connected speech (VPC-Rate). In both scales, higher scores indicated a more severe velopharyngeal insufficiency. RESULTS: No difference between surgical groups was shown. A low positive correlation was found between posterior cleft width and VPC-Rate (Spearman = .23; P = .025). The role of the covariate "cleft size at tuberosity level" was confirmed in an ordinal logistic regression model (odds ratio [OR] = 1.17; 95% confidence interval [CI]:1.01-1.35). A low negative correlation was shown between anteroposterior palatal length and VPC-Sum (Spearman = -.27; P = .004) and confirmed by the pooled scores VPC-Pooled (OR = 0.82; 95% CI: 0.69-0.98) and VPC-Dichotomic (OR = 0.82; 95% CI: 0.68-0.99). CONCLUSIONS: Posterior cleft dimensions can be a modest indicator for the prognosis of velopharyngeal function at age 5 years, when the soft palate is closed first, independently on the timing of hard palate repair. Antero-posterior palatal length seems to protect from velopharyngeal insufficiency and hypernasality. However, the association found was significant but low.

Oxidative stress-alleviating strategies to improve recombinant protein production in CHO cells.

Large scale biopharmaceutical production of biologics relies on the overexpression of foreign proteins by cells cultivated in stirred tank bioreactors. It is well recognized and documented fact that protein overexpression may impact host cell metabolism and that factors associated with large scale culture, such as the hydrodynamic forces and inhomogeneities within the bioreactors, may promote cellular stress. The metabolic adaptations required to support the high-level expression of recombinant proteins include increased energy production and improved secretory capacity, which, in turn, can lead to a rise of reactive oxygen species (ROS) generated through the respiration metabolism and the interaction with media components. Oxidative stress is defined as the imbalance between the production of free radicals and the antioxidant response within the cells. Accumulation of intracellular ROS can interfere with the cellular activities and exert cytotoxic effects via the alternation of cellular components. In this context, strategies aiming to alleviate oxidative stress generated during the culture have been developed to improve cell growth, productivity, and reduce product microheterogeneity. In this review, we present a summary of the different approaches used to decrease the oxidative stress in Chinese hamster ovary cells and highlight media development and cell engineering as the main pathways through which ROS levels may be kept under control.

Application of a genome-scale model in tandem with enzyme assays for identification of metabolic signatures of high and low CHO cell producers.

Biopharmaceutical industrial processes are based on high yielding stable recombinant Chinese Hamster Ovary (CHO) cells that express monoclonal antibodies. However, the process and feeding regimes need to be adapted for each new cell line, as they all have a slightly different metabolism and product performance. A main limitation for accelerating process development is that the metabolic pathways underlying this physiological variability are not yet fully understood. This study describes the evolution of intracellular fluxes during the process for 4 industrial cell lines, 2 high producers and 2 low producers (n = 3), all of them producing a different antibody. In order to understand from a metabolic point of view the phenotypic differences observed, and to find potential targets for improving specific productivity of low producers, the analysis was supported by a tailored genome-scale model and was validated with enzymatic assays performed at different days of the process. A total of 59 reactions were examined from different key pathways, namely glycolysis, pentose phosphate pathway, TCA cycle, lipid metabolism, and oxidative phosphorylation. The intracellular fluxes did not show a metabolic correlation between high producers, but the degree of similitude observed between cell lines could be confirmed with additional experimental observations. The whole analysis led to a better understanding of the metabolic requirements for all the cell lines, allowed to the identification of metabolic bottlenecks and suggested targets for further cell line engineering. This study is a successful application of a curated genome-scale model to multiple industrial cell lines, which makes the metabolic model suitable for process platform.

Genus level analysis of PKS-NRPS and NRPS-PKS hybrids reveals their origin in Aspergilli.

BACKGROUND: Filamentous fungi produce a vast amount of bioactive secondary metabolites (SMs) synthesized by e.g. hybrid polyketide synthase-nonribosomal peptide synthetase enzymes (PKS-NRPS; NRPS-PKS). While their domain structure suggests a common ancestor with other SM proteins, their evolutionary origin and dynamics in fungi are still unclear. Recent rational engineering approaches highlighted the possibility to reassemble hybrids into chimeras - suggesting molecular recombination as diversifying mechanism. RESULTS: Phylogenetic analysis of hybrids in 37 species - spanning 9 sections of Aspergillus and Penicillium chrysogenum - let us describe their dynamics throughout the genus Aspergillus. The tree topology indicates that three groups of PKS-NRPS as well as one group of NRPS-PKS hybrids developed independently from each other. Comparison to other SM genes lead to the conclusion that hybrids in Aspergilli have several PKS ancestors; in contrast, hybrids are monophyletic when compared to available NRPS genes - with the exception of a small group of NRPSs. Our analysis also revealed that certain NRPS-likes are derived from NRPSs, suggesting that the NRPS/NRPS-like relationship is dynamic and proteins can diverge from one function to another. An extended phylogenetic analysis including bacterial and fungal taxa revealed multiple ancestors of hybrids. Homologous hybrids are present in all sections which suggests frequent horizontal gene transfer between genera and a finite number of hybrids in fungi. CONCLUSION: Phylogenetic distances between hybrids provide us with evidence for their evolution: Large inter-group distances indicate multiple independent events leading to the generation of hybrids, while short intra-group distances of hybrids from different taxonomic sections indicate frequent horizontal gene transfer. Our results are further supported by adding bacterial and fungal genera. Presence of related hybrid genes in all Ascomycetes suggests a frequent horizontal gene transfer between genera and a finite diversity of hybrids - also explaining their scarcity. The provided insights into relations of hybrids and other SM genes will serve in rational design of new hybrid enzymes.

Reprogramming AA catabolism in CHO cells with CRISPR/Cas9 genome editing improves cell growth and reduces byproduct secretion.

Chinese hamster ovary (CHO) cells are the preferred host for producing biopharmaceuticals. Amino acids are biologically important precursors for CHO metabolism; they serve as building blocks for proteogenesis, including synthesis of biomass and recombinant proteins, and are utilized for growth and cellular maintenance. In this work, we studied the physiological impact of disrupting a range of amino acid catabolic pathways in CHO cells. We aimed to reduce secretion of growth inhibiting metabolic by-products derived from amino acid catabolism including lactate and ammonium. To achieve this, we engineered nine genes in seven different amino acid catabolic pathways using the CRISPR-Cas9 genome editing system. For identification of target genes, we used a metabolic network reconstruction of amino acid catabolism to follow transcriptional changes in response to antibody production, which revealed candidate genes for disruption. We found that disruption of single amino acid catabolic genes reduced specific lactate and ammonium secretion while specific growth rate and integral of viable cell density were increased in many cases. Of particular interest were Hpd and Gad2 disruptions, which show unchanged AA uptake rates, while having growth rates increased up to 19%, and integral of viable cell density as much as 50% higher, and up to 26% decrease in specific ammonium production and to a lesser extent (up to 22%) decrease in lactate production. This study demonstrates the broad potential of engineering amino acid catabolism in CHO cells to achieve improved phenotypes for bioprocessing.

BCAT1 and BCAT2 disruption in CHO cells has cell line-dependent effects.

In recombinant protein expression using Chinese hamster ovary (CHO) cells, chemically defined media contain essential amino acids such as branched chain amino acids (BCAAs) leucine, isoleucine and valine. Availability of amino acids is critical as these are building blocks for protein synthesis. However, breakdown of amino acids can lead to build up of toxic intermediates and metabolites that decrease cell growth, productivity and product quality. BCAA catabolism also hampers the usage of BCAAs for protein synthesis. In this work we studied the effects of disrupting the genes responsible for the first step of BCAA catabolism: branched chain aminotransferase 1 (Bcat1) and branched chain aminotransferase 2 (Bcat2). We evaluated the effect of disrupting the genes individually and in combination, and examined the effects in producer and non-producer host cells. Our experiments show that Bcat1 disruption improves cell growth in producer cells, but not in non-producers. Conversely, Bcat2 has a minor negative effect on growth in producer cells, and none in non-producers. Combined Bcat1 and Bcat2 disruption improves growth in producer cells. By-product metabolism is cell line-, clone- and producer-dependent. Overall, our results show that the effects of targeting Bcat1 and/or Bcat2 are cell line-dependent, and seemingly linked to the burden of recombinant protein expression.

Strategies to establish the link between biosynthetic gene clusters and secondary metabolites.

Filamentous fungi produce a vast number of bioactive secondary metabolites (SMs), some of which have found applications in the pharmaceutical industry including as antibiotics and immunosuppressants. As more and more species are whole genome sequenced the number of predicted clusters of genes for SM biosynthesis is ever increasing - holding a promise of novel useful bioactive SMs. To be able to fully utilize the potential of novel SMs, it is necessary to link the SM and the genes responsible for producing it. This can be challenging, but many strategies and tools have been developed for this purpose. Here we provide an overview of the methods used to establish the link between SM and biosynthetic gene cluster (BGC) and vice versa, along with the challenges and advantages of each of the methods. Part I of the review, associating BCG with SM, is divided into gene manipulations native strain and heterologous expression strategies, depending on the fungal species. Part II, associating SM with BGC, is divided into three main approaches: (1) homology search (2) retro-biosynthesis and (3) comparative genomics.

Scandcleft Project, Trial 1: Comparison of Speech Outcome in Relation to Timing of Hard Palate Closure in 5-Year-Olds With UCLP.

OBJECTIVE: To compare in-depth speech results in Scandcleft Trial 1 as well as reference data from peers without cleft palate (CP). DESIGN: A prospective randomized clinical trial. SETTING: A Danish and a Swedish CP center. PARTICIPANTS: 143 of 148 randomized 5-year-olds with unilateral cleft lip and palate. All received lip and velum closure at 4 months, and hard palate closure at 12 months (arm A) or 36 months (arm B). MAIN OUTCOME MEASURES: A composite measure based on velopharyngeal competence (VPC) or velopharyngeal incompetence (VPI), an overall assessment of VPC from connected speech (VPC-Rate), Percentage of Consonants Correct (PCC-score), and consonant errors. Speech therapy visits, average hearing thresholds, and secondary pharyngeal surgeries documented burden of treatment. RESULTS: Across the trial, 61.5% demonstrated VPC and 38.5% VPI. Twenty-two percent of participants achieved age appropriate PCC-scores. There were no statistically significant differences between arms or centers for these measures. In the Danish center, arm B: achieved lower PCC-scores (P = .01); obtained PCC-scores without s-errors below 79% (P = .002); produced ≥3 active oral cleft speech characteristics (P = .004) than arm A. In both centers, arm B attended more speech visits. CONCLUSIONS: At age 5, differences between centers and treatment arms were not statistically significant for VPC/VPI, but consonant proficiency differed between treatment arms in the Danish center. Poor speech outcomes were seen for both treatment arms. Variations between centers were observed. As the Swedish center had few participants, intercenter comparisons should be interpreted with caution.

Genetic engineering approaches to improve posttranslational modification of biopharmaceuticals in different production platforms.

The number of approved biopharmaceuticals, where product quality attributes remain of major importance, is increasing steadily. Within the available variety of expression hosts, the production of biopharmaceuticals faces diverse limitations with respect to posttranslational modifications (PTM), while different biopharmaceuticals demand different forms and specifications of PTMs for proper functionality. With the growing toolbox of genetic engineering technologies, it is now possible to address general as well as host- or biopharmaceutical-specific product quality obstacles. In this review, we present diverse expression systems derived from mammalians, bacteria, yeast, plants, and insects as well as available genetic engineering tools. We focus on genes for knockout/knockdown and overexpression for meaningful approaches to improve biopharmaceutical PTMs and discuss their applicability as well as future trends in the field.

Resistance Gene-Directed Genome Mining of 50 Aspergillus Species.

Fungal secondary metabolites are a rich source of valuable natural products, and genome sequencing has revealed a proliferation of predicted biosynthetic gene clusters in the genomes. However, it is currently an unfeasible task to characterize all biosynthetic gene clusters and to identify possible uses of the compounds. Therefore, a rational approach is needed to identify a short list of gene clusters responsible for producing valuable compounds. To this end, several bioactive clusters include a resistance gene, which is a paralog of the target gene inhibited by the compound. This mechanism can be used to identify these clusters. We have developed the FRIGG (fungal resistance gene-directed genome mining) pipeline for identifying this type of biosynthetic gene cluster based on homology patterns of the cluster genes. In this work, the FRIGG pipeline was run using 51 Aspergillus and Penicillium genomes, identifying 72 unique families of putative resistance genes. The pipeline also identified the previously characterized resistance gene inpE from the fellutamide B cluster, thereby validating the approach. We have successfully developed an approach to identify putative valuable bioactive clusters based on a specific resistance mechanism. This approach will be highly useful as an ever-increasing amount of genomic data becomes available; the art of identifying and selecting the right clusters producing novel valuable compounds will only become more crucial. IMPORTANCE Species belonging to the Aspergillus genus are known to produce a large number of secondary metabolites; some of these compounds are used as pharmaceuticals, such as penicillin, cyclosporine, and statin. With whole-genome sequencing, it became apparent that the genetic potential for secondary metabolite production is much larger than expected. As an increasing number of species are whole-genome sequenced, thousands of secondary metabolite genes are predicted, and the question of how to selectively identify novel bioactive compounds from this information arises. To address this question, we have created a pipeline to predict genes involved in the production of bioactive compounds based on a resistance gene hypothesis approach.

Systematic Evaluation of Site-Specific Recombinant Gene Expression for Programmable Mammalian Cell Engineering.

Many branches of biology depend on stable and predictable recombinant gene expression, which has been achieved in recent years through targeted integration of the recombinant gene into defined integration sites. However, transcriptional levels of recombinant genes in characterized integration sites are controlled by multiple components of the integrated expression cassette. Lack of readily available tools has inhibited meaningful experimental investigation of the interplay between the integration site and the expression cassette components. Here we show in a systematic manner how multiple components contribute to final net expression of recombinant genes in a characterized integration site. We develop a CRISPR/Cas9-based toolbox for construction of mammalian cell lines with targeted integration of a landing pad, containing a recombinant gene under defined 5' proximal regulatory elements. Generated site-specific recombinant cell lines can be used in a streamlined recombinase-mediated cassette exchange for fast screening of different expression cassettes. Using the developed toolbox, we show that different 5' proximal regulatory elements generate distinct and robust recombinant gene expression patterns in defined integration sites of CHO cells with a wide range of transcriptional outputs. This approach facilitates the generation of user-defined and product-specific gene expression patterns for programmable mammalian cell engineering.