An accessible insight into genetic findings for transplantation recipients with suspected genetic kidney disease

Evaluation for genetic disease in kidney transplant candidates: A practice resource

The increasing availability of clinically approved genetic tests for kidney disease has spurred the growth in the use of these tests in kidney transplant practice. Neither the testing options nor the patient population where this should be deployed has been defined, and its value in kidney transplant evaluation has not been demonstrated. Transplant providers may not always be aware of the limitations of genetic testing and may need guidance on comprehending test results and providing counsel, as many centers do not have easy access to a renal genetic counselor or a clinical geneticist. In this practice resource, a working group of nephrologists, geneticists, and a genetic counselor provide a pragmatic, tailored approach to genetic testing, advocating for its use only where the genetic diagnosis or its exclusion can impact the choices available for transplantation or posttransplant management or the workup of living donor candidates at increased risk for heritable disease.

Emerging role of genetics in kidney transplantation

The advent of more affordable genomic analytical pipelines has facilitated the expansion of genetic studies in kidney transplantation. Advances in genetic sequencing have allowed for a greater understanding of the genetic basis of chronic kidney disease, which has helped to guide transplant management and address issues related to living donation in specific disease settings. Recent efforts have shown significant effects of genetic ancestry and donor APOL1 risk genotypes in determining worse allograft outcomes and increased donation risks. Genetic studies in kidney transplantation outcomes have started to assess the effects of donor and recipient genetics in primary disease recurrence and transplant-related comorbidities, while genome-wide donor-recipient genetic incompatibilities have been shown to represent an important determinant of alloimmunity. Future large-scale comprehensive studies will shed light on the clinical utility of integrative genomics in the kidney transplantation setting.

Monogenic Kidney Diseases in Adults With Chronic Kidney Disease (CKD)

BACKGROUND

According to current evidence, every 10th to 11th adult with chronic kidney disease (CKD) has a monogenic disease of the kidney.

METHODS

This review is based on reported studies in which molecular genetic diagnostic techniques were used to investigate monogenic kidney diseases in adults with CKD. The studies were identified by a selective literature search using predefined criteria.

RESULTS

In 12 selected studies, diagnostic variants of 179 different genes were identified in 1467 out of 6607 study participants with CKD (22.2%). More than 60% of these variants affected 8 genes (PKD1, PKD2, COL4A3, COL4A4, COL4A5, UMOD, MUC1, HNF1B). Three diseases are associated with these genes: autosomal dominant polycystic kidney disease (ADPKD), Alport syndrome, and autosomal dominant tubulo-interstitial kidney disease (ADTKD). Physicians treating patients with CKD should be alert to the presence of any red flags, such as onset at a young age, a positive family history, or hematuria of unknown cause. When a genetic etiology is suspected, a specialized work-up is indicated, often including a molecular genetic investigation. A positive genetic finding usually leads to a modification of the patient's specific diagnosis and/or treatment.

CONCLUSION

Awareness of the high prevalence of monogenic kidney diseases in adults with CKD and alertness to their suggestive clinical features are crucial for the timely initiation of targeted diagnostic testing. The molecular genetic identification of these diseases is a prerequisite for appropriate patient management.

Genetic testing in pediatric kidney transplant recipients to promote informed choice and improve individualized monitoring

BACKGROUND

The growing body of research on kidney disease in children has identified a broad spectrum of genetic etiologies.

METHODS

We conducted a prospective study to evaluate the efficacy of an optimized genetic test and subclinical changes in a real-world context before kidney transplantation. All cases involved recipients under the age of 18 who underwent whole exome sequencing (ES) between 2013 and 2022.

RESULTS

The study population included 244 children, with a median age of 13.1 years at transplantation. ES provided a molecular genetic diagnosis in 114 (46.7%) probands with monogenic variants in 15 known disease-causing genes. ES confirmed the suspected clinical diagnosis in 74/244 (30.3%) cases and revised the pre-exome clinical diagnoses in 40/244 (16.4%) cases. ES also established a specific underlying cause for kidney failure for 19 patients who had previously had an unknown etiology. Genetic diagnosis influenced clinical management in 88 recipients (36.1%), facilitated genetic counseling for 18 families (7.4%), and enabled comprehensive assessment of living donor candidates in 35 cases (14.3%).

CONCLUSIONS

Genetic diagnosis provides critical insights into the pathogenesis of kidney disease, optimizes clinical strategies concerning risk assessment of living donors, and enhances disease surveillance of recipients.

Early prediction of growth patterns after pediatric kidney transplantation based on height-related single-nucleotide polymorphisms

BACKGROUND

Growth retardation is a common complication of chronic kidney disease in children, which can be partially relieved after renal transplantation. This study aimed to develop and validate a predictive model for growth patterns of children with end-stage renal disease (ESRD) after kidney transplantation using machine learning algorithms based on genomic and clinical variables.

METHODS

A retrospective cohort of 110 children who received kidney transplants between May 2013 and September 2021 at the First Affiliated Hospital of Zhengzhou University were recruited for whole-exome sequencing (WES), and another 39 children who underwent transplant from October 2021 to March 2022 were enrolled for external validation. Based on previous studies, we comprehensively collected 729 height-related single-nucleotide polymorphisms (SNPs) in exon regions. Seven machine learning algorithms and 10-fold cross-validation analysis were employed for model construction.

RESULTS

The 110 children were divided into two groups according to change in height-for-age Z -score. After univariate analysis, age and 19 SNPs were incorporated into the model and validated. The random forest model showed the best prediction efficacy with an accuracy of 0.8125 and an area under curve (AUC) of 0.924, and also performed well in the external validation cohort (accuracy, 0.7949; AUC, 0.796).

CONCLUSIONS

A model with good performance for predicting post-transplant growth patterns in children based on SNPs and clinical variables was constructed and validated using machine learning algorithms. The model is expected to guide clinicians in the management of children after renal transplantation, including the use of growth hormone, glucocorticoid withdrawal, and nutritional supplementation, to alleviate growth retardation in children with ESRD.

Genetic testing in the evaluation of recipient candidates and living kidney donors

PURPOSE OF REVIEW

The aim of this study is to provide an overview of the role of genetic testing in the evaluation of kidney transplant candidates and living donors who may be at risk for heritable kidney disease. We focus our discussion on monogenic diseases, excluding renal diseases that have complex polygenic influences. Adoption of new technologies such as next-generation sequencing (NGS) with comprehensive gene panels has greatly enabled access to genetic testing recently; yet transplant professionals rarely receive adequate training in clinical genetics. In addition to a broad discussion of genetic testing, we hope to illustrate the thought processes and resources used in clinical genetic evaluation of recipient candidates and donors.

RECENT FINDINGS

Targeted renal genetic panels, whole exome and genome sequencing have greatly expanded our ability to test for pathogenic variants. Testing methods, analytic tools and the subsequent interpretation by the testing laboratory and treating physician impacts patient management and clinicians may lack the resources to practice in this new era of genomic medicine.

SUMMARY

The expansion of genomics into transplant medicine can provide improved diagnosis in transplant candidates and potentially disease prediction in living donors. Transplant professionals need to be familiar with emerging trends, promises and limitations of NGS-based testing.

Population pharmacokinetics of mycophenolate mofetil in pediatric patients early after liver transplantation

Objective: To investigate the factors influencing the pharmacokinetics of mycophenolate mofetil (MMF) in pediatric patients after liver transplantation, and to establish a population pharmacokinetics model, which can provide a reference for clinical dosage adjustment.

Methods: A prospective study in a single center was performed on pediatric patients who were administrated with mycophenolate mofetil dispersible tablets (MMFdt) for at least 4 days after liver transplantation continuously. Blood samples were collected in ethylene diamine tetraacetic acid anticoagulant tubes before dosing and 0.5, 1, 2, 4, 8, and 12 h after the morning intake of MMFdt. The concentrations of mycophenolic acid (MPA) in plasma were assayed with a validated reverse-phase high-performance liquid chromatography method. UGT1A8 518C > G, UGT1A9 -275T > A, UGT1A9 -2152C > T, UGT2B7 211G > T, SLC O 1B1 521T > C polymorphism were determined by Sanger sequencing. Nonlinear mixed effects modeling was used to establish the population pharmacokinetics (PPK) model. The predictability and stability of the model were internally evaluated by the goodness of fit plots, visual prediction check, normalized prediction errors, and bootstraps.

Results: A two-compartment model with first-order absorption and first-order elimination was established with 115 MPA concentrations from 20 pediatric patients. The final model were: CL/F (L/h) = 14.8×(WT/7.5)^0.75×(DOSE/11.16)^0.452×е^0.06, Ka (h⁻¹) = 2.02×(WT/7.5)^−0.25, Vc/F (L) = 6.01×(WT/7.5), Vp/F (L) = 269 (fixed), Q/F (L/h) = 15.4×(WT/7.5)^0.75×е^1.39. Where CL/F was the apparent clearance rate, Ka was the absorption rate constant, Vc/F was the apparent distribution volume of the central compartment, Vp/F was the apparent distribution volume of the peripheral compartment, Q/F was the atrioventricular clearance rate, WT was the body weight of the subject, and DOSE was the MMFdt administered dose. The model indicated there was large inter-individual variability in CL/F and Q/F after multiple dosing of MMFdt. Internal evaluation results showed that the final model had good stability and prediction performance.

Conclusion: A stable and predictive population pharmacokinetic model of MMFdt in pediatric patients after the early stage of liver transplantation was established. The pediatric patient’s weight and the dose of MMFdt can be a reference to adjust the MMFdt dose.

The HIDDEN Protocol: An Australian Prospective Cohort Study to Determine the Utility of Whole Genome Sequencing in Kidney Failure of Unknown Aetiology

Early identification of genetic kidney disease allows personalised management, clarification of risk for relatives, and guidance for family planning. Genetic disease is underdiagnosed, and recognition of genetic disease is particularly challenging in patients with kidney failure without distinguishing diagnostic features. To address this challenge, the primary aim of this study is to determine the proportion of genetic diagnoses amongst patients with kidney failure of unknown aetiology, using whole genome sequencing (WGS). A cohort of up to 100 Australian patients with kidney failure of unknown aetiology, with onset <50 years old and approved by a panel of study investigators will be recruited via 18 centres nationally. Clinically accredited WGS will be undertaken with analysis targeted to a priority list of ∼388 genes associated with genetic kidney disease. The primary outcome will be the proportion of patients who receive a molecular diagnosis (diagnostic rate) via WGS compared with usual -care (no further diagnostic investigation). Participant surveys will be undertaken at consent, after test result return and 1 year subsequently. Where there is no or an uncertain diagnosis, future research genomics will be considered to identify candidate genes and new pathogenic variants in known genes. All results will be relayed to participants via the recruiting clinician and/or kidney genetics clinic. The study is ethically approved (HREC/16/MH/251) with local site governance approvals in place. The future results of this study will be disseminated and inform practical understanding of the potential monogenic contribution to kidney failure of unknown aetiology. These findings are anticipated to impact clinical practice and healthcare policy.