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<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2021-03-03T03:15:59.1669819+00:00 -->
<!-- Version            : 5.0.1.571 -->
<!-- Package ID         : b5829f5324954692a51592b439ef90d5 -->
<!-- Copyright (c) 2021 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="tsha_SeriesAAchievementOfSpecificClinicalMilestoneTwoMember" name="SeriesAAchievementOfSpecificClinicalMilestoneTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_SeriesAUponAchievementOfCertainDefinedClinicalMilestonesMember" name="SeriesAUponAchievementOfCertainDefinedClinicalMilestonesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_PBMTGTHoldingsLimitedLiabilityCompanyMember" name="PBMTGTHoldingsLimitedLiabilityCompanyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_NolanCapitalLimitedLiabilityCompanyMember" name="NolanCapitalLimitedLiabilityCompanyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_SeriesBPurchaseAgreementMember" name="SeriesBPurchaseAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_MeasurementInputProbabilityOfAchievingClinicalMilestonesAndTimingMember" name="MeasurementInputProbabilityOfAchievingClinicalMilestonesAndTimingMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_ProceedsFromIssuanceOfCommonStockGross" name="ProceedsFromIssuanceOfCommonStockGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="tsha_ConvertiblePreferredStockTrancheLiabilityOfferingPrice" name="ConvertiblePreferredStockTrancheLiabilityOfferingPrice" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="tsha_ConvertiblePreferredStockTrancheLiabilityMeasurementInput" name="ConvertiblePreferredStockTrancheLiabilityMeasurementInput" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="tsha_ConvertiblePreferredStockTrancheLiabilityLiquidityTerm" name="ConvertiblePreferredStockTrancheLiabilityLiquidityTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_PreferredStockTrancheLiability" name="PreferredStockTrancheLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="tsha_IssuanceOfProRataPortionOfMilestoneShares" name="IssuanceOfProRataPortionOfMilestoneShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_MileStoneSharesIssued" name="MileStoneSharesIssued" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_AmountReclassifiedToConvertiblePreferredStock" name="AmountReclassifiedToConvertiblePreferredStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="tsha_PreferredStockTrancheLiabilityMember" name="PreferredStockTrancheLiabilityMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_TwoThousandTwentyStockIncentivePlanMember" name="TwoThousandTwentyStockIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_CertainEmployeesAndConsultantsMember" name="CertainEmployeesAndConsultantsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_ShareBasedCompensationAwardTrancheFourMember" name="ShareBasedCompensationAwardTrancheFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_ShareBasedCompensationArrangementByShareBasedPaymentAwardCommencementDate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardCommencementDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_PercentageOfAutomaticIncreaseEveryYearInCommonStockSharesReservedForFutureIssuance" name="PercentageOfAutomaticIncreaseEveryYearInCommonStockSharesReservedForFutureIssuance" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="tsha_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReplacementUnitsGrantsInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReplacementUnitsGrantsInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_CommonStockFairValuePerShare" name="CommonStockFairValuePerShare" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="tsha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodIntrinsicValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodIntrinsicValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReplacementUnitsGrantsInPeriodWeightedAverageGrantDateFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReplacementUnitsGrantsInPeriodWeightedAverageGrantDateFairValue" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_IncomeTaxDisclosureLineItems" name="IncomeTaxDisclosureLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_IncomeTaxDisclosureTable" name="IncomeTaxDisclosureTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_NetOperatingLossCarryforwardPercentage" name="NetOperatingLossCarryforwardPercentage" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_TaxCutsAndJobsActAdjustedTaxableIncomeLimitationPercentage" name="TaxCutsAndJobsActAdjustedTaxableIncomeLimitationPercentage" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_EffectiveIncomeTaxRateReconciliationGeneralBusinessCredits" name="EffectiveIncomeTaxRateReconciliationGeneralBusinessCredits" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences" name="EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_EffectiveIncomeTaxRateReconciliationChangeInFairValueOfTrancheLiability" name="EffectiveIncomeTaxRateReconciliationChangeInFairValueOfTrancheLiability" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_DeferredTaxAssetsOrganizationalAndStartUpCosts" name="DeferredTaxAssetsOrganizationalAndStartUpCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="tsha_TaxCreditCarryforwardExpirationOrDueDateYear" name="TaxCreditCarryforwardExpirationOrDueDateYear" type="us-types:gYearListItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_OperatingLeasesInitialDirectCosts" name="OperatingLeasesInitialDirectCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="tsha_OfficeSpaceAreaUnderLeaseAgreement" name="OfficeSpaceAreaUnderLeaseAgreement" type="num:areaItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_ExtendingTermOfLease" name="ExtendingTermOfLease" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="tsha_DallasLeaseMember" name="DallasLeaseMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="tsha_PegasusParkLLCMember" name="PegasusParkLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</xsd:schema>
